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 | Physical Review BWelcome to the new web site of Physical Review B, the APS journal devoted to condensed matter and materials physics. Our goal is to publish the most important, stimulating, and useful papers for our international community of researchers spanning many subdisciplines. We hope that our new web site will provide an intuitive and efficient way to access those papers plus information about the journal. We welcome your comments and suggestions. Please email them to feedback@aps.org. More...
Magnetism Grégoire Misguich, Vincent Pasquier, and Fabien Alet The three-dimensional classical dimer model with interactions shows an unexpected continuous phase transition between an ordered dimer crystal and a Coulomb liquid. A detailed analysis of the critical dimer and monomer correlation functions points to a subtle interplay between the fluctuations of th... [Phys. Rev. B 78, 100402 ] Published Wed Sep 3, 2008 Read articleJ. Spałek, A. Kozłowski, Z. Tarnawski, Z. Kąkol, Y. Fukami, F. Ono, R. Zach, L. J. Spalek, and J. M. Honig We provide evidence for the existence of a quantum critical point at the metallization of magnetite Fe3O4 at pressure pc≈8 GPa . We show that the present ac magnetic-susceptibility data support earlier resistivity data. The Verwey temperature scales with pressure TV∼(1−p/pc)ν with νâ... [Phys. Rev. B 78, 100401 ] Published Tue Sep 2, 2008 Read articleF. Moussa, M. Hennion, A. Gukasov, S. Petit, L. P. Regnault, A. Ivanov, R. Suryanarayanan, M. Apostu, and A. Revcolevschi The bilayer manganite La1.2Sr1.8Mn2O7 (LSMO) exhibits a phase transition from a paramagnetic insulating (PI) to a ferromagnetic metallic (FM) state with a colossal magnetoresistance (CMR) effect. Upon 60% Pr substitution, both the magnetic order and the PI to FM transition are suppressed. However,... [Phys. Rev. B 78, 060406 ] Published Wed Aug 20, 2008 Read articleC. v. Korff Schmising, A. Harpoeth, N. Zhavoronkov, Z. Ansari, C. Aku-Leh, M. Woerner, T. Elsaesser, M. Bargheer, M. Schmidbauer, I. Vrejoiu, D. Hesse, and M. Alexe  [Phys. Rev. B 78, 060404 ] Published Mon Aug 18, 2008 Read articleSergei Urazhdin We use a combination of analytical calculations and numerical simulations to demonstrate that electrical current flowing through a magnetic bilayer induces dynamical coupling between the layers. The coupling originates from the dependence of the spin transfer torque on the relative orientations of t... [Phys. Rev. B 78, 060405 ] Published Mon Aug 18, 2008 Read articleV. V. Khovaylo, K. P. Skokov, Yu. S. Koshkid’ko, V. V. Koledov, V. G. Shavrov, V. D. Buchelnikov, S. V. Taskaev, H. Miki, T. Takagi, and A. N. Vasiliev A comprehensive study of the adiabatic temperature change ΔTad in the vicinity of a first-order magnetostructural phase transition has been carried out on a Ni2.19Mn0.81Ga Heusler alloy. It was found that the directly measured ΔTad∼1 K is of order of magnitude smaller than that expected ... [Phys. Rev. B 78, 060403 ] Published Thu Aug 14, 2008 Read articleSuperfluidity and superconductivity N. Suresh, J. G. Storey, G. V. M. Williams, and J. L. Tallon We have carried out measurements of the pressure dependence to 1.2 GPa of the oxygen isotope effect on Tc in the high- Tc superconductor YBa2Cu4O8 using a clamp cell in a superconducting quantum interference device magnetometer. This compound lies close to, but just above, the 1/8th doping po... [Phys. Rev. B 78, 100503 ] Published Fri Sep 5, 2008 Read articleC. Krellner, N. Caroca-Canales, A. Jesche, H. Rosner, A. Ormeci, and C. Geibel Resistivity, specific-heat, and magnetic-susceptibility measurements performed on SrFe2As2 samples evidence a behavior very similar to that observed in LaFeAsO and BaFe2As2 , with the difference being that the formation of the spin-density wave and the lattice deformation occur in a pronounced fi... [Phys. Rev. B 78, 100504 ] Published Fri Sep 5, 2008 Read articleT. Sato, K. Terashima, K. Nakayama, S. Souma, T. Takahashi, T. Yamamoto, and K. Kadowaki We have performed ultrahigh energy- and momentum-resolved angle-resolved photoemission spectroscopy of impurity-doped Bi2Sr2CaCu2O8 . We found that the point node of the superconducting gap near the (π/2,π/2) point in a pristine sample gradually evolves into a small gapless Fermi arc upon Zn or... [Phys. Rev. B 78, 100502 ] Published Thu Sep 4, 2008 Read articleK. Ahilan, F. L. Ning, T. Imai, A. S. Sefat, R. Jin, M. A. McGuire, B. C. Sales, and D. Mandrus We report on 19F nuclear magnetic resonance (NMR) investigation of the high-temperature superconductor LaFeAsO0.89F0.11 (Tc∼28 K) . We demonstrate that low-frequency spin fluctuations exhibit pseudogap behavior above Tc . We also deduce the London penetration depth λ from NMR line broad... [Phys. Rev. B 78, 100501 ] Published Wed Sep 3, 2008 Read articleAndrey Chubukov and Ilya Eremin [Phys. Rev. B 78, 060509 ] Published Fri Aug 29, 2008 Read articleJ. Málek, S.-L. Drechsler, U. Nitzsche, H. Rosner, and H. Eschrig The optical conductivity σ(ω) is calculated at finite temperature T for CuO2 chain clusters within a pd -Hubbard model. Data at T=300 K for Li2CuO2 are reanalyzed within this approach. The relative weights of Zhang-Rice singlet and triplet charge excitations near 2.5 and 4 eV, respect... [Phys. Rev. B 78, 060508 ] Published Wed Aug 27, 2008 Read articleB. Wiendlocha, J. Tobola, M. Sternik, S. Kaprzyk, K. Parlinski, and A. M. Oleś Superconductivity in Mo3Sb7 is analyzed using the combined electronic structure and phonon calculations, and the electron-phonon coupling constant λph=0.54 is determined from first principles. This value explains the experimental value of the superconducting critical temperature Tc=2.2 K . T... [Phys. Rev. B 78, 060507 ] Published Mon Aug 25, 2008 Read articleAlaska Subedi, David J. Singh, and Mao-Hua Du We report first-principles calculations of the electronic structure, phonon dispersions, and electron-phonon coupling of LaNiPO. These calculations show that this material can be explained as a conventional electron-phonon superconductor in contrast to the FeAs based high-temperature superconductors... [Phys. Rev. B 78, 060506 ] Published Wed Aug 20, 2008 Read articleZheng Li, Gengfu Chen, Jing Dong, Gang Li, Wanzheng Hu, Dan Wu, Shaokui Su, Ping Zheng, Tao Xiang, Nanlin Wang, and Jianlin Luo A series of layered nickel-based LaNiAsO1−xFx compounds with x=0–0.15 are synthesized by solid-state reactions. The pure LaNiAsO exhibits bulk superconductivity with Tc∼2.75 K . Partial substitution of oxygen with fluorine increases the transition temperature to ∼3.8 K . The LaNiA... [Phys. Rev. B 78, 060504 ] Published Mon Aug 18, 2008 Read articleJoshua H. Tapp, Zhongjia Tang, Bing Lv, Kalyan Sasmal, Bernd Lorenz, Paul C. W. Chu, and Arnold M. Guloy The synthesis and properties of LiFeAs, a high- Tc Fe-based superconducting stoichiometric compound, are reported. Single crystal x-ray studies reveal that it crystallizes in the tetragonal PbFCl type (P4/nmm) with a=3.7914(7) Å and c=6.364(2) Å . Unlike the known isoelectronic undoped int... [Phys. Rev. B 78, 060505 ] Published Mon Aug 18, 2008 Read articleA. P. Litvinchuk, V. G. Hadjiev, M. N. Iliev, Bing Lv, A. M. Guloy, and C. W. Chu Polarized Raman spectra of nonsuperconducting SrFe2As2 and superconducting K0.4Sr0.6Fe2As2 (Tc=37 K) microcrystals are reported. All four-phonon modes (A1g+B1g+2Eg) allowed by symmetry are found and identified. Shell model gives reasonable description of the spectra. No detectable anomalie... [Phys. Rev. B 78, 060503 ] Published Thu Aug 14, 2008 Read articleE. Khatami, A. Macridin, and M. Jarrell We study the effect of long-range hoppings on Tc for the two-dimensional (2D) Hubbard model with and without Holstein phonons using parameters evaluated from band-structure calculations for cuprates. Employing the dynamical cluster approximation (DCA) with a quantum Monte Carlo (QMC) cluster solve... [Phys. Rev. B 78, 060502 ] Published Fri Aug 8, 2008 Read articleElectronic structure: wide-band, narrow-band, and strongly correlated systems David J. Cho, Feng Wang, Xiang Zhang, and Y. Ron Shen Optical metamaterials can exhibit negative index of refraction when both the effective permittivity and permeability are negative. The negative permeability is usually considered to be associated with a magnetic dipole resonance and the contribution from electric quadrupoles is neglected. Here, we s... [Phys. Rev. B 78, 121101 ] Published Thu Sep 4, 2008 Read articleAthanasios N. Chantis, R. C. Albers, M. D. Jones, Mark van Schilfgaarde, and Takao Kotani We present results for the electronic structure of α -uranium using a recently developed quasiparticle self-consistent GW (QSGW) method. This is the first time that the f -orbital electron-electron interactions in an actinide have been treated by a first-principles method beyond the level of the ... [Phys. Rev. B 78, 081101 ] Published Wed Aug 13, 2008 Read articleSemiconductors II: surfaces, interfaces, microstructures, and related topics M. Vladimirova, S. Cronenberger, P. Barate, D. Scalbert, F. J. Teran, and A. P. Dmitriev Time-resolved Kerr rotation experiments show that two kinds of spin modes exist in diluted magnetic semiconductor quantum wells: (i) strongly coupled electron-magnetic ion spin excitations and (ii) excitations of magnetic ion spin subsystem decoupled from electron spins. The coexistence of these two... [Phys. Rev. B 78, 081305 ] Published Mon Aug 25, 2008 Read articleH. Kumano, H. Kobayashi, S. Ekuni, Y. Hayashi, M. Jo, H. Sasakura, S. Adachi, S. Muto, and I. Suemune High degree of excitonic spin-state preservation during energy relaxation is demonstrated in a single quantum dot. Optical-phonon resonances and corresponding suppression of spin relaxation are clearly identified as dip structures in photoluminescence excitation spectra probed by the positive trion ... [Phys. Rev. B 78, 081306 ] Published Mon Aug 25, 2008 Read articleAnabela G. Rolo, Mikhail I. Vasilevskiy, Mimoun Hamma, and Carlos Trallero-Giner In contrast to the most commonly studied nanocrystals of II-VI materials, resonant Raman spectra of colloidal III-V quantum dots (QDs) show two almost equally intense peaks centered approximately at the longitudinal and transverse optical (TO) bulk phonon frequencies. The “anomalous” spectra of ... [Phys. Rev. B 78, 081304 ] Published Mon Aug 18, 2008 Read articleJi Young Lee, Jin-Ho Choi, and Jun-Hyung Cho Scanning tunneling microscopy experiments reported that desorption from the hydrogen- and halogen-terminated Si(001) surfaces exhibits frequently the two types of dangling-bond (DB) configurations. One is the intradimer configuration, where two DBs are within a single Si dimer, and the other is the ... [Phys. Rev. B 78, 081303 ] Published Thu Aug 14, 2008 Read articleSurface physics, nanoscale physics, low-dimensional systems B. Huard, N. Stander, J. A. Sulpizio, and D. Goldhaber-Gordon [Phys. Rev. B 78, 121402 ] Published Thu Sep 4, 2008 Read articleHongki Min, Rafi Bistritzer, Jung-Jung Su, and A. H. MacDonald Because graphene is an atomically two-dimensional gapless semiconductor with nearly identical conduction and valence bands, graphene-based bilayers are attractive candidates for high-temperature electron-hole pair condensation. We present estimates which suggest that the Kosterlitz-Thouless temperat... [Phys. Rev. B 78, 121401 ] Published Wed Sep 3, 2008 Read articleM. Suri and T. Dumitrică Large-scale atomistic simulations considering a 5 nm in radius H-passivated Si nanosphere that impacts with relatively low energies onto a H-passivated Si substrate reveal a transition between two fundamental collision modes. At impacting speeds of less than ∼1000 m/s particle-reflection domin... [Phys. Rev. B 78, 081405 ] Published Tue Aug 26, 2008 Read articleMichele Lazzeri, Claudio Attaccalite, Ludger Wirtz, and Francesco Mauri We compute the electron-phonon coupling (EPC) of selected phonon modes in graphene and graphite using various ab initio methods. The inclusion of nonlocal exchange-correlation effects within the GW approach strongly renormalizes the square EPC of the A1′ K mode by almost 80% with respect to ... [Phys. Rev. B 78, 081406 ] Published Tue Aug 26, 2008 Read articleYun-Song Zhou, Ben-Yuan Gu, Sheng Lan, and Li-Ming Zhao We present the time-domain analysis of the extraordinary optical transmission of the slits milled on the thin metallic film. We employ the finite-difference time-domain method to study the variations of the transmission energies with the sampling time received by several monitors that are placed on ... [Phys. Rev. B 78, 081404 ] Published Fri Aug 22, 2008 Read articleDirect visualization of charge distributions during femtosecond laser ablation of a Si (100) surface Christoph T. Hebeisen, Germán Sciaini, Maher Harb, Ralph Ernstorfer, Sergei G. Kruglik, and R. J. Dwayne Miller We directly observe the charge distributions and resulting electric fields present during the earliest stages of laser ablation of a Si (100) surface by using femtosecond electron pulses as a probe. We find the magnitude of the field to be 3.5×106 V/m just 3 ps after an excitation pulse of 5.6... [Phys. Rev. B 78, 081403 ] Published Thu Aug 14, 2008 Read articleRecently published articles in Physical Review B. See the current issues for more. Superfluidity and superconductivity N. Suresh, J. G. Storey, G. V. M. Williams, and J. L. Tallon  We have carried out measurements of the pressure dependence to 1.2 GPa of the oxygen isotope effect on Tc in the high- Tc superconductor YBa2Cu4O8 using a clamp cell in a superconducting quantum interference device magnetometer. This compound lies close to, but just above, the 1/8th doping po... [Phys. Rev. B 78, 100503 ] Published Fri Sep 5, 2008 Read articleC. Krellner, N. Caroca-Canales, A. Jesche, H. Rosner, A. Ormeci, and C. Geibel Resistivity, specific-heat, and magnetic-susceptibility measurements performed on SrFe2As2 samples evidence a behavior very similar to that observed in LaFeAsO and BaFe2As2 , with the difference being that the formation of the spin-density wave and the lattice deformation occur in a pronounced fi... [Phys. Rev. B 78, 100504 ] Published Fri Sep 5, 2008 Read articleÁ. Pallinger, B. Sas, I. Pethes, K. Vad, F. I. B. Williams, and G. Kriza Pulsed high-current experiments in single crystals of the high- Tc superconductor Bi2Sr2CaCu2O8+δ in a c -axis-directed magnetic field H reveal that the ab -face resistance in the free flux flow regime is a solely logarithmic function of H , devoid of any power-law component. Reanalysis of ... [Phys. Rev. B 78, 104502 ] Published Fri Sep 5, 2008 Read articleSemiconductors II: surfaces, interfaces, microstructures, and related topics Tsai-Yu Huang, C.-T. Liang, Gil-Ho Kim, C. F. Huang, Chao-Ping Huang, Jyun-Ying Lin, Hsi-Sheng Goan, and D. A. Ritchie We have performed low-temperature transport measurements on a GaAs two-dimensional electron system at low magnetic fields. Multiple temperature-independent points and accompanying oscillations are observed in the longitudinal resistivity between the low-field insulator and the quantum Hall (QH) liqu... [Phys. Rev. B 78, 113305 ] Published Fri Sep 5, 2008 Read articleA. V. Rodina and A. Yu. Alekseev We present Maxwell equations with source terms for the electromagnetic field interacting with a moving electron in a spin-orbit-coupled semiconductor heterostructure. We start with the eight-band kp model and derive the electric and magnetic polarization vectors using the Gordon-type decomposition... [Phys. Rev. B 78, 115304 ] Published Fri Sep 5, 2008 Read articleAngélica S. Mata, Silvio C. Ferreira, Igor R. B. Ribeiro, and Sukarno O. Ferreira CdTe films grown on glass substrates covered by fluorine-doped tin oxide by hot-wall epitaxy were studied through the interface dynamical scaling theory. Direct measures of the dynamical exponent revealed an intrinsically anomalous scaling characterized by a global roughness exponent α , distinct ... [Phys. Rev. B 78, 115305 ] Published Fri Sep 5, 2008 Read articleOleksandr Zelyak and Ganpathy Murthy We study the persistent current of noninteracting electrons subject to a pointlike magnetic flux in the simply connected chaotic Robnik-Berry quantum billiard and also in an annular analog thereof. For the simply connected billiard, we find a large diamagnetic contribution to the persistent current ... [Phys. Rev. B 78, 125305 ] Published Thu Sep 4, 2008 Read articleOrsolya Kálmán, Péter Földi, Mihály G. Benedict, and F. M. Peeters Electron transport through multiterminal rectangular arrays of quantum rings is studied in the presence of Rashba-type spin-orbit interaction (SOI) and of a perpendicular magnetic field. Using the analytic expressions for the transmission and reflection coefficients for single rings we obtain the co... [Phys. Rev. B 78, 125306 ] Published Thu Sep 4, 2008 Read articleStructure, structural phase transitions, mechanical properties, defects Erell Bonnot, Eduard Vives, Lluís Mañosa, Antoni Planes, and Ricardo Romero In the present paper, by using a specially designed experiment, we analyze the relationship between the acoustic emission and the deformation resulting from front propagation during a stress-induced transition from cubic to a single-variant martensite in a Cu-Zn-Al single crystal. The front propagat... [Phys. Rev. B 78, 094104 ] Published Fri Sep 5, 2008 Read articleY. Pennec, B. Djafari-Rouhani, H. Larabi, J. O. Vasseur, and A. C. Hladky-Hennion We investigate theoretically the band structure of a phononic crystal of finite thickness constituted of a periodical array of cylindrical dots deposited on a thin plate of a homogeneous material. We show that this structure can display a low-frequency gap, as compared to the acoustic wavelengths in... [Phys. Rev. B 78, 104105 ] Published Fri Sep 5, 2008 Read articleInhomogeneous, disordered, and partially ordered systems Kostya Trachenko We calculate the energy and heat capacity of a liquid on the basis of its elastic properties and vibrational states. The experimental decrease of liquid heat capacity with temperature is attributed to the increasing loss of two transverse modes with frequency ω<1/τ , where τ is liquid relax... [Phys. Rev. B 78, 104201 ] Published Fri Sep 5, 2008 Read articleMagnetism Gang Chen and Leon Balents We consider spin-orbit coupling effects in Na4Ir3O8 , a material in which Ir4+ spins form an hyper-kagome lattice, a three-dimensional network of corner-sharing triangles. We argue that both low-temperature thermodynamic measurements and the impurity susceptibility induced by dilute substitution ... [Phys. Rev. B 78, 094403 ] Published Fri Sep 5, 2008 Read articleY. Huttel, E. Navarro, N. D. Telling, G. van der Laan, F. Pigazo, F. J. Palomares, C. Quintana, E. Roman, G. Armelles, and A. Cebollada We show that Fe nanoislands capped with Al, Pd, and Pt protecting layers include an alloy at the interface with the capping layer, which explains the previously known capping layer dependence on the interparticle magnetic coupling. Vibrating sample magnetometry results, for instance, are evidencing ... [Phys. Rev. B 78, 104403 ] Published Fri Sep 5, 2008 Read articleElectronic structure: wide-band, narrow-band, and strongly correlated systems Sébastien Dusuel, Kai Phillip Schmidt, Julien Vidal, and Rosa Letizia Zaffino We analyze the Kitaev model on the triangle-honeycomb lattice whose ground state has recently been shown to be a chiral spin liquid. We consider two perturbative expansions: the isolated-dimer limit containing Abelian anyons and the isolated-triangle limit. In the former case, we derive the low-ener... [Phys. Rev. B 78, 125102 ] Published Fri Sep 5, 2008 Read articleMinh-Tien Tran The Keldysh boundary problem in a nonequilibrium Falicov-Kimball model in infinite dimensions is studied within the truncated and self-consistent perturbation theories and the dynamical mean-field theory. Within the model the system is started in equilibrium, and later a uniform electric field is tu... [Phys. Rev. B 78, 125103 ] Published Fri Sep 5, 2008 Read articleDavid J. Cho, Feng Wang, Xiang Zhang, and Y. Ron Shen Optical metamaterials can exhibit negative index of refraction when both the effective permittivity and permeability are negative. The negative permeability is usually considered to be associated with a magnetic dipole resonance and the contribution from electric quadrupoles is neglected. Here, we s... [Phys. Rev. B 78, 121101 ] Published Thu Sep 4, 2008 Read articleMasahiko Higuchi and Katsuhiko Higuchi We present a pair density (PD) functional scheme utilizing the noninteracting reference system. In order to check to what extent this scheme can express the correlation effects, actual calculations are performed for the neutral neon atom. It is shown that this scheme reproduces about 20% of the corr... [Phys. Rev. B 78, 125101 ] Published Thu Sep 4, 2008 Read articleSurface physics, nanoscale physics, low-dimensional systems V. Zólyomi, J. Koltai, J. Kürti, and S. Pekker We present a first-principles study of the electronic structure of fullerene-cubane cocrystals, using density-functional theory at the local-density approximation level. The band structure is calculated along high-symmetry lines and compared with that of the fcc fullerene. We also present a study of... [Phys. Rev. B 78, 115405 ] Published Fri Sep 5, 2008 Read articleMarkus Müller, Lars Fritz, and Subir Sachdev We study the thermal and electric transport of a fluid of interacting Dirac fermions using a Boltzmann approach. We include Coulomb interactions, a dilute density of charged impurities, and the presence of a magnetic field to describe both the static and the low-frequency response as a function of t... [Phys. Rev. B 78, 115406 ] Published Fri Sep 5, 2008 Read articleMaría Belén Franzoni, Patricia R. Levstein, Jésus Raya, and Jérôme Hirschinger NMR experiments in C60 reveal the origin of the “pseudocoherence” that leads to long tails in some Carr-Purcell-Meiboom-Gill (CPMG) sequences in contrast with the decay of a standard Hahn echo. We showed in a previous work [M. B. Franzoni and P. R. Levstein, Phys. Rev. B 72, 235410 (2005)] tha... [Phys. Rev. B 78, 115407 ] Published Fri Sep 5, 2008 Read articleS. K. Bose, R. Sharma, and R. C. Budhani Spin-dependent charge transport in a two-tier granular system consisting of mesoscopic Fe plaquettes over which silver nanospheres are dispersed is investigated. This system transits from a Coulomb blockade regime with a finite voltage threshold for charge flow to an infinitely connected network sho... [Phys. Rev. B 78, 115403 ] Published Thu Sep 4, 2008 Read articleYong-Ju Kang, Joongoo Kang, and K. J. Chang First-principles calculations show that the electronic structure of graphene on SiO2 strongly depends on the surface polarity and interface geometry. Surface dangling bonds mediate the coupling to graphene and can induce hole or electron doping via charge transfer even in the absence of extrinsic ... [Phys. Rev. B 78, 115404 ] Published Thu Sep 4, 2008 Read articleB. Huard, N. Stander, J. A. Sulpizio, and D. Goldhaber-Gordon We perform electrical transport measurements in graphene with several sample geometries. In particular, we design “invasive” probes crossing the whole graphene sheet as well as “external” probes connected through graphene side arms. The four-probe conductance measured between external probes... [Phys. Rev. B 78, 121402 ] Published Thu Sep 4, 2008 Read articleL. S. Froufe-Pérez and R. Carminati Coupling a single dipole emitter to a metallic nanoparticle through the optical modes of a planar superlens made of left-handed material can lead to substantial modifications of its spontaneous decay rate. We provide a quantitative study based on exact numerical simulation and show that such a schem... [Phys. Rev. B 78, 125403 ] Published Thu Sep 4, 2008 Read articlePapers recently accepted for publication in Physical Review B (view more). Structure, structural phase transitions, mechanical properties, defects, etc. SrTiO_{3} and BaTiO_{3} revisited using the projector augmented wave method: Performance of hybrid and semilocal functionals Roman Wahl, Doris Vogtenhuber and Georg Kresse The structural, electronic and phonon properties of the cubic and tetragonal phase of SrTiO3 and BaTiO3 are studied from ab initio. The calculations are performed in the projector augmented wave (PAW) density functional theory (DFT) framework using the local density approximation (LDA), gradient corrected functionals (PBE, PBEsol) and hybrid functional (HSE) as implemented in the Vienna ab initio simulation package (VASP). Due to the large variation of theoretical predictions for the frequency of the G15 (TO1) zone-center phonon mode (94i - 64 cm-1) special attention is accorded to this particular mode and its volume dependence. Accepted Fri Sep 5, 2008 Kink pair nucleation on dislocations under stress in the two dimensional Frenkel Kontorova model David Rodney and Laurent Proville We present static and dynamic simulations to study the thermally-activated motion of dislocations. The model employed is the two-dimensional Frenkel-Kontorova model, the main interest of which is to allow simulations of dislocation dynamics over long time periods ( ~ 600 ns), giving access to large ranges of applied stresses and temperatures. The kink-pair nucleation rates, determined from dynamical simulations, are studied as a function of the ratio between the kink-pair activation enthalpy and the thermal energy. The former is computed from static simulations based on the Elastic Nudged Band (NEB) method. We show here that the dislocation motion is composed of two regimes: a low-temperature regime where the nucleation rate follows a thermally-activated exponential law and a high-temperature regime where the motion is slower than expected from the low-temperature exponential law. We evidence a correlation between successive dislocation jumps that stems from the dynamics of internal modes of the dislocation and impedes high-frequency nucleation events. Accepted Fri Sep 5, 2008 Size dependent characterization of embedded Ge nanocrystals: Structural and thermal properties L. L. Araujo, R. Giulian, D. J. Sprouster, C. S. Schnohr, D. J. Llewellyn, P. Kluth, D. J. Cookson, G. J. Foran and M. C. Ridgway A combination of conventional and synchrotron-based techniques has been used to characterize the growth and size-dependent structural properties of Ge nanocrystals (Ge NCs) embedded in an amorphous silica (a-SiO2) matrix. Ge NC size distributions with four different diameters ranging from 4 to 9 nm were produced by ion implantation and thermal annealing and characterized with small-angle X-ray scattering and transmission electron microscopy. An Ostwald ripening growth regime was operative for all samples. The NCs were well represented by the superposition of bulk-like crystalline and amorphous environments suggesting the formation of an amorphous layer separating the crystalline NC core and the a-SiO2 matrix. The amorphous fraction was quantified with X-ray absorption near-edge spectroscopy and increased as the NC diameter decreased consistent with the increase in surface-to-volume ratio. The structural parameters of the first three nearest-neighbor shells were determined with extended X-ray absorption fine structure spectroscopy and evolved linearly with inverse NC diameter. Specifically, an increase in total disorder, interatomic distance and the asymmetry in the distribution of distances were observed as the NC size decreased demonstrating finite-size effects govern the structural properties of embedded Ge NCs. Such results are compared to previous reports and discussed in terms of the influence of the surface-to-volume ratio in objects of nanometer dimensions. Accepted Fri Sep 5, 2008 Electronic structure: wide-band, narrow-band, and strongly correlated systems Reply to ``Comment on `Resonant inelastic x-ray scattering of MnO: L_{2,3} edge measurements and assessment of their interpretation' '' G. Ghiringhelli, M. Matsubara, C. Dallera, F. Fracassi, A. Tagliaferri, N. B. Brookes, A. Kotani and L. Braicovich In their comment to our recent paper [Phys. Rev. B 73, 035111 (2006)], Müller and Hüfner propose a comparison of our Mn L2,3 RIXS data with low energy EELS measurements. The differences in the experimental spectra highlighted by the authors can be easily ascribed to the different cross sections in the two techniques, even when they probe the same subset of excited states, namely the dd excitations. One important difference is that EELS is limited to quartet final states only, whereas RIXS can lead to doublets too. Thus our theoretical interpretation of the RIXS spectra, made within two different models, is compatible with the traditional crystal field analysis of EELS. As the Sugano-Tanabe diagram usually do not include the 3d spin-orbit and the inter-atomic super-exchange interactions, their accuracy is limited to hundreds of meV and they should be utilized only for rough assignments of the spectral features. On the contrary, by calculating the RIXS spectral shape we could address more sophisticated models with remarkable agreement to the experimental results. This is hardly possible in the case of low energy EELS, for which reliable simulations of the spectra are much more difficult. Accepted Fri Sep 5, 2008 Phase separation in the two dimensional repulsive Hubbard model ChiaChen Chang and Shiwei Zhang Using recent advances in auxiliary-field quantum Monte Carlo techniques and the phaseless approximation to control the sign/phase problem, we determine the equation of state in the ground state of the two-dimensional repulsive single-band Hubbard model at intermediate interactions. Finite-size and shell effects are eliminated by boundary condition integration. Spin-spin correlation functions and structure factors are also calculated. The results show clear signal for phase-separation. Upon doping, the system separates into one phase of density n=1 (hole-free) and the other at density nc ( ~ 0.9). The long-range antiferromagnetic order is coupled to this process, and is lost below nc. Accepted Fri Sep 5, 2008 Inhomogeneous, disordered, and partially ordered systems Influence of fabrication disorder on the optical properties of coupled cavity photonic crystal waveguides D. P. Fussell, S. Hughes and M. M. Dignam Employing a tight-binding formalism and perturbation theory, we theoretically demonstrate how weak fabrication disorder due to surface roughness dramatically reduces the bandedge performance of coupled-cavity waveguides in semiconductor photonic crystal slabs. We find that surface roughness largely affects the bandedge performance through the introduction of random variations in the individual cavity frequencies, W0, rather than through variations in the tight-binding coupling-coefficients, k. Using model roughness parameters comparable to state-of-the-art structures, the standard deviation of W0 is estimated to be sw0 >~10-4W0. High-index-contrast fabrication imperfections are found to broaden the photon density of states at the bandedge with a characteristic linewidth of ge sw04/3/(2W0k)1/3. This implies a minimal bandedge group velocity of around vg ~ c/120, consistent with experiments. For applications towards modified spontaneous emission, we show that the characteristic linewidth ge is, unfortunately, a factor of 5 greater than the largest bandedge coupling-rate for which strong photon-quantum dot bandedge interactions can occur. Although large Purcell factors can still be achieved in the presence of disorder, an embedded semiconductor quantum-dot then couples to a lossy (disorder-induced) propagation mode, which may limit the potential applications in coherent quantum optics. Accepted Fri Sep 5, 2008 Semiconductors I: bulk First principles study of Fe and FeAl defects in SiGe alloys A. Carvalho, J. Coutinho, R. Jones, J. Goss, M. Barroso and P. R. Briddon First-principles, spin-polarized local density functional calculations are used to model interstitial iron () and its complexes with substitutional aluminum in dilute SixGe1-x alloys (x < 8%). We considered both the effect of direct bonding between or FeiAl with Ge atoms in the x0 limit and the evolution of the defect properties with the alloy composition. It is found that prefers Si-rich regions, but when placed near a Ge atom, its (0/+) level is shifted towards the conduction band. However, the ionization energy of Fe(+/+2)-Al- is only slightly changed by the presence of neighboring Ge atoms in the proximity. It is also found that indirect alloying effects shift the donor levels of and FeAl at a fast rate towards the valence band. The acceptor levels, however, remain approximately at the same distance from Ev. Accepted Fri Sep 5, 2008 Dynamics, dynamical systems, lattice effects, quantum solids, etc. Generalized density of-states and anharmonicity of the low energy phonon bands from coherent inelastic neutron scattering response in the \beta-phase pyrochlore osmates AOs_{2}O_{6} (A=K, Rb, Cs) Hannu Mutka, Michael Marek Koza, Mark Robert Johnson, Zenji Hiroi, JunIchi Yamaura and Yohei Nagao Inelastic neutron scattering on powder samples has been employed to investigate the lattice dynamics of alkali metal osmates. We have obtained the neutron weighted generalized phonon density of states from momentum transfer averaged coherent inelastic response. We have paid special attention to the low-energy modes that have been assigned to the Einstein term of the lattice specific heat and from which a 'rattling' behavior of the alkali atoms has been inferred. In all of the three compounds our results reveal a split band with two prominent peaks in the low-energy range associated with the vibrational modes of A-atoms. The temperature dependence of these bands has been followed in the range from 1.5 K < T < 300 K. The strongest temperature effect is visible in the case of KOs2O6, the split band peaking at (h/2p)w 5.5 meV and 6.8 meV at T= 300 K softens on cooling resulting in a main band at about (h/2p)w 3.4 meV at T <~50 K, while a smaller softening of D((h/2p)w) < 1 meV is seen in the other two compounds. In agreement with earlier work the temperature dependent modifications of the phonon spectrum can be attributed to the weak potential felt by the A-atom in the oversized cage where it is located. At low-T the characteristic energies for each of the compounds are well correlated with the specific heat observations published earlier. The powder averaged phonon response shows Q-dependence indicating coherent coupling of the alkali atom vibrations with the rest of the lattice. Accepted Fri Sep 5, 2008 Noise induced Bessel like oscillations of Shapiro steps with the period of the ac force Jasmina Tekic and Hu Bambi The frequency dependence of the dynamical-mode locking phenomena in the presence of noise is studied in the one-dimensional ac driven dissipative Frenkel-Kontorova model. It was found that besides producing the melting of the Shapiro steps and decrease of the critical depinning force, noise may transfer system by decreasing the dc threshold value into the high amplitude regime where the oscillations of the step width with the frequency of ac force will appear. Expressed as a function of the ac period, these oscillations have the Bessel-like form, the same as the well known Bessel-like oscillations with amplitude. They may appear in any real system, irrespectively of the numbers of degrees of freedom, and strongly affect the stability of the Shapiro steps that is of great importance in the technical applications of interference effects. Accepted Fri Sep 5, 2008 Generalized Langevin equation for solids. I. Rigorous derivation and main properties L. Kantorovich We demonstrate explicitly that the derivation by Adelman and Doll (AD) [J. Chem. Phys., v. 64, p. 2375 (1976)] of the Generalized Langevin Equation (GLE) to describe dynamics of an extended solid system by considering its finite subsystem, is inconsistent because it relies on performing statistical averages over the entire system when establishing properties of the random force. This results in the random force representing a non-stationary process, opposite to one of the main assumptions made in AD that the random force corresponds to a stationary stochastic process. This invalidates the derivation of the Brownian (or Langevin) form of the GLE in AD. Here we present a different and more general approach in deriving the GLE. Our method generalizes that of AD in two main aspects: (i) the structure of the finite region can be arbitrary (e.g. anharmonic) and (ii) ways are indicated in which the method can be implemented exactly if the phonon Green's function of the harmonic environment region, surrounding the anharmonic region, is known which is e.g. the case when the environment region represents a part of a periodic solid (the bulk or a surface). We also show that in general, after the local perturbation has ceased, the system returns to thermodynamic equilibrium with the distribution function for region 1 being canonical with respect to an effective interaction between atoms which includes instantaneous response of the surrounding region. Note that our method does not rely on the assumption made in AD that the stochastic force correlation function depends on the times difference only (i.e. the random force corresponds to a stationary random process). In fact, we demonstrate explicitly that generally this is not the case. Still, the correct GLE can be obtained which satisfies exactly the fluctuation-dissipation theorem. Accepted Fri Sep 5, 2008 Generalized Langevin equation for solids. II. Stochastic boundary conditions for nonequilibrium molecular dynamics simulations L. Kantorovich and N. Rompotis The Generalized Langevin Equation (GLE) [L. Kantorovich - Phys. Rev. B (2008) submitted], which describes dynamics of a finite and possibly highly anharmonic subsystem surrounded by an extended harmonic solid, is simplified here assuming short-range interactions between atoms. We show that in this case quite naturally the GLE can be worked into a form which corresponds to considering central atoms of the finite region as governed by usual Newtonian mechanics, while the boundary atoms are treated as Langevin atoms, i.e. they experience friction and random forces (the so-called Stochastic Boundary Conditions, SBC). We show that the random forces constitute a stationary Gaussian random process with the dispersion directly related to the friction coefficient in a usual way. Next, we rigorously demonstrate that, even though not all atoms are stochastic within the SBC model, the system should still arrive at canonical distribution at long times. Since the SBC model follows directly from the general GLE description and can perform as a correct NVT thermostat, we propose that the SBC is a method of choice if one wants to do non-equilibrium MD simulations correctly. Our derivation of SBC is physically more acceptable than given previously when the central region atoms were assumed to be much heavier than those in the surrounding lattice (the zero-frequency approximation). Accepted Fri Sep 5, 2008 Semiconductors II: surfaces, interfaces, microstructures, and related topics Theory of valence band holes as Luttinger spinors in vertically coupled quantum dots J. I. Climente, M. Korkusinski, G. Goldoni and P. Hawrylak We describe the valence band holes of quantum dot molecules formed by two vertically coupled disks, using a 4-band k·p Hamiltonian. It is shown that the strong spin-orbit coupling of the valence band introduces characteristic features in the hole tunneling which are not captured by the usual single-band heavy hole approximation. Therefore, a treatment of hole states as multi-band Luttinger spinors is required. Within this description the parity symmetry in the vertical direction is lost, and chirality symmetry must be used instead. Effects of spin-orbit coupling on the hole and exciton states, as well as on the optical transitions are discussed. We show that, with increasing interdot distance, the spin-orbit interaction leads to a bonding-antibonding ground state transition and to quenching of the excitonic emission. These results are relevant to recent experiments. Accepted Fri Sep 5, 2008 Magnetism Weak ferromagnetism accompanying loop current order in underdoped cuprate superconductors Vivek Aji, Arkady Shekhter and C. M. Varma We discuss the necessary symmetry conditions, and the different ways in which they can be physically realized, for the occurrence of ferromagnetism accompanying the loop-current orbital magnetic order observed by polarized neutron diffraction experiments (or indeed any other conceivable principal order) in the underdoped phase of cuprates. We contrast the Kerr effect experiments in single crystals observing ferromagnetism with the direct magnetization measurements in large powder samples, which do not observe it. We also suggest experiments to resolve the differences among the experiments, all of whom we believe to be correct. Accepted Fri Sep 5, 2008 \textit{Ab initio} theoretical study of magnetization and phase stability of the (Fe,Co,Ni)_{23}B_{6} and (Fe,Co,Ni)_{23}Zr_{6} structures of Cr_{23}C_{6} and Mn_{23}Th_{6} prototypes Ohodnicki Jr. P. R., N. Cates, D. E. Laughlin, M. E. McHenry and M. Widom We present an Ab-Initio theoretical investigation of the magnetic properties and phase stability of two different complex cubic structures of prototype Cr23C6 and Mn23Th6, with an emphasis on the (Fe,Co,Ni)23B6 and (Fe,Co,Ni)23Zr6 compositions. These phases have recently been observed as secondary or even primary crystallization products of (Fe,Co,Ni)-Zr-B and related metallic glasses that have been studied for applications as soft magnets with nanocrystalline grain size. We first demonstrate the validity of the theoretical technique employed through a detailed comparison between the predictions of the calculations for the Co-Zr binary system and the experimentally stable phases. We then investigate the magnetic properties and stability of the binary phases. While the Fe-based binary Fe23Zr6 and Fe23B6 phases are expected to have the highest magnetization, the Co-based binary Co23Zr6 and Co23B6 structures are predicted to be the most stable of each prototype. The Co23Zr6 structure is the only binary 23:6 structure predicted to be a stable phase for the (Fe,Co,Ni)23B6 and (Fe,Co,Ni)23Zr6 systems investigated here. Small additions of Zr atoms to the (Fe,Co,Ni)23B6 phases tend to substitutionally occupy the 8c Wykoff site and stabilize these structures. In contrast, small additions of B to the (Fe,Co,Ni)23Zr6 phases have a much weaker site preference and tend to destabilize these structures. As a result, (Fe,Co,Ni)23B6 structures are stabilized in (Fe,Co,Ni)-Zr-B systems relative to the binary (Fe,Co,Ni)23B6 systems while the (Fe,Co,Ni)23Zr6 phases are not. The results presented in this work are in good qualitative agreement with experimental observations of the compositional modifications tending to promote formation of the 23:6 phases in Fe-Co-Zr-B and related metallic glasses. Accepted Fri Sep 5, 2008 Magnetism and chemical ordering in binary transition metal clusters Georg Rollmann, Sanjubala Sahoo, Alfred Hucht and Peter Entel Binary XY clusters, with X, Y {Mn, Fe, Co, Ni}, are investigated within first-principles simulations in the framework of density functional theory. In the case of Co-Mn, the increase in magnetic moment with Mn concentration, which is in contrast to the bulk behavior and was also observed experimentally, is explained on the basis of the electronic structure of the clusters. For Co-Fe, Ni-Mn, Ni-Fe, and Ni-Co, due to the ferromagnetic couplings between the local moments, the same dependence is found, i.e., moments increasing with the concentration of the element with the lower value of atomic number. For Fe-Mn (as well as Co-Mn and Ni-Mn clusters containing many Mn atoms), the situation appears to be more complex with antiferromagnetic tendencies resulting in a nonmonotonic change of the cluster moment with Mn concentration. Accepted Fri Sep 5, 2008 Antisymmetric exchange interactions in Ni_{4} clusters N. Kirchner, van Slageren van Slageren J., B. Tsukerblat, O. Waldmann and M. Dressel We show that in molecular Ni4 clusters with S4 symmetry not only the local anisotropy, but also the antisymmetric exchange interaction contributes to the observed fourth-order anisotropy terms in the single-spin Hamiltonian. From a group theoretical classification of the exchange-coupled multiplets, the effective spin Hamiltonian terms are determined. We find that low-lying excited spin states possess an orbital angular momentum, which mixes into the spin ground state, leading to a effective antisymmetric exchange term. The simulation of the magnetic and spectroscopic experimental data allowed the extraction of parameter values for all interactions. Accepted Fri Sep 5, 2008 Surface physics, low-dimensional systems, and related topics Kekule distortion-induced exciton instability in graphene Raoul Dillenschneider Effects of a Kekule distortion on exciton instability in single-layer graphene are discussed. In the framework of quantum electrodynamics the mass of the electron generated dynamically is worked out using a Schwinger-Dyson equation. For homogeneous lattice distortion it is shown that the generated mass is independent of the amplitude of the lattice distortion at the one-loop approximation. Formation of excitons induced by the homogeneous Kekule distortion could appear only through direct dependence of the lattice distortion. Accepted Fri Sep 5, 2008 Interaction and concerted diffusion of lithium in a (5,5) carbon nanotube M. Khantha, N. A. Cordero, J. A. Alonso, M. Cawkwell and L. A. Girifalco The interaction of lithium atoms inside and outside a (5,5) carbon nanotube is studied using density functional theory. The Li-nanotube interaction is compared with the Li-graphene interaction calculated using the same technique. As expected from the tubular geometry, the binding energy of Li with the nanotube is higher than its binding energy with graphene. In the repulsive region, the interactions of Li with both the tube and graphene are nearly identical but they differ in the attractive part. The Li-Li interaction when both Li atoms are inside the nanotube is calculated. At small separations between the Li atoms, the repulsive interaction is a screened Coulomb potential. However, at larger separations, the Li-Li interaction does not vanish and shows residual oscillations. The net repulsive long-range interaction has a profound effect on the diffusion of Li inside the tube. The activation barrier for concerted diffusion of several Li atoms is much smaller than the diffusion barrier for individual atoms. Thus, concerted diffusion is likely to occur compared to the independent diffusion of individual Li. Accepted Fri Sep 5, 2008 Nonequilibrium carriers in graphene under interband photoexcitation A. Satou, F. T. Vasko and V. Ryzhii We study nonequilibrium carriers (electrons and holes) in an intrinsic graphene at low temperatures under far- and mid-infrared (IR) radiation in a wide range of its intensities. The energy distributions of carriers are calculated using a quasiclassical kinetic equation which accounts for the energy relaxation due to acoustic phonons and the radiative generation-recombination processes associated with thermal radiation and the carrier photoexcitation by incident radiation. It is found that the nonequilibrium distributions are determined by an interplay between weak energy relaxation on acoustic phonons and generation-recombination processes as well as by the effect of pumping saturation. Due to the effect of saturation, the carrier distribution functions can exhibit plateaus around the pumping region at elevated intensities. As shown, at sufficiently strong mid-IR pumping, the population inversion can occur below the pumping energy. The graphene dc conductivity as a function of the pumping intensity exhibits a pronounced nonlinearity with a sub-linear region at fairly low intensities and a saturation at a strong pumping. However, an increase in the pumping intensity in very wide range leads only to a modest increase in the carrier concentration and, particularly, the dc conductivity. The graphene conductivity at mid-IR irradiation exhibit strong sensitivity to mechanisms of carrier momentum relaxation. Accepted Fri Sep 5, 2008 Magnetic structure of periodically meandered one dimensional Fe nanowires Susumu Shiraki, Hideki Fujisawa, Tetsuya Nakamura, Takayuki Muro, Masashi Nantoh and Maki Kawai Magnetism in one-dimensional (1D) Fe nanowires grown on Au(788) is investigated by x-ray magnetic circular dichroism. The long-range ferromagnetic order breaks into spin-blocks at the elevated temperature due to enhanced fluctuation in the 1D system. The average block size rapidly decreases as the temperature increases, following the Arrhenius law ruled by exchange energy and the number of antiparallel spin pairs at the boundaries. We also found a gradual change in magnetization processes depending on the coverage: from site-by-site motion of spin-block boundaries toward pinning of the boundaries at the narrow positions of the wires resulting in flips of giant spins inside the blocks. Accepted Fri Sep 5, 2008 Superfluidity and superconductivity Magnetization and Cu nuclear magnetic resonance study of Sr_{0.9}La_{0.1}Cu_{1-x}Ni_{x}O_{2} G. V. M. Williams, S. Richter, J. Haase, C. U. Jung, HyeGyong Lee and SungIk Lee We report the results from a Cu nuclear magnetic resonance (NMR) and magnetization study of the electron-doped high temperature superconducting cuprate (HTSC) Sr0.9La0.1Cu1-xNixO2. This compound shows a large suppression of superconductivity by Ni (delta Tc/delta x=18 K/hole-doped HTSCs. We find small effective moments of 0.06 B/Cu for the pure sample and 0.76 B/Ni for the 1regime. The partial substitution of Ni for Cu causes the Cu NMR linewidth to increase and there is a further reduction in the Cu NMR intensity with decreasing temperature over and above that observed in the pure compound. This can be interpreted in terms of Ni inducing additional spin disorder and wipeout of the Cu NMR intensity for Cu sites near the Ni impurities. Accepted Fri Sep 5, 2008 Field angle dependent thermal conductivity in nodal superconductors Abu Alrub T. R. and S. H. Curnoe We apply a semi-classical method to the problem of field angle-dependent oscillations of the density of states and thermal conductivity for nodal superconductors and apply our results to the superconductor . The oscillatory contributions to the thermal conductivity for all possible point node configurations for a superconductor with Th symmetry are calculated. It is found that experimental results are best accounted for by nodes in the off-axis directions [sinf0, 0,cosf0], which are associated with the time-reversal breaking, triplet paired phase with symmetry D2(E). Accepted Fri Sep 5, 2008 Local density approximation and dynamical mean field theory of optical weights and photoemission spectra of doped charge transfer insulators Cedric Weber, Kristjan Haule and Gabriel Kotliar We use the Local Density Approximation in combination with the Dynamical Mean Field Theory to investigate intermediate energy properties of the copper oxides. We identify coherent and incoherent spectral features that results from doping a charge transfer insulator, namely quasiparticles, Zhang-Rice singlet band, and the upper and lower Hubbard bands. Angle resolving these features, we identify a waterfall like feature, between the quasiparticle part and the incoherent part of the Zhang-Rice band. We investigate the asymetry between particle and hole doping. On the hole doped side, there is a very rapid transfer of spectral weight upon doping in the one particle spectra. The optical spectral weight increases superlinearly on the hole doped side in agreement with experiments. Accepted Fri Sep 5, 2008 Effects of Zn and Ni substitution on the Cu spin dynamics and superconductivity in La_{2-x}Sr_{x}Cu_{1-y}(Zn,Ni)_{y}O_{4} (x=0.15--0.20): Muon spin relaxation and magnetic susceptibility study T. Adachi, N. Oki, Risdiana, S. Yairi, Y. Koike and I. Watanabe We have investigated effects of Zn and Ni on the Cu-spin dynamics and superconductivity from the zero-field muon-spin-relaxation (ZF-mSR) and magnetic-susceptibility, c, measurements for La2-xSrxCu1-y(Zn,Ni)yO4 with x = 0.15- 0.20, changing y up to 0.10 in fine step. In the optimally doped x=0.15, it has been concluded that the formation of a magnetic order requires a larger amount of Ni than that of Zn, which is similar to our previous results of x = 0.13. From the estimation of volume fractions of superconducting (SC) and magnetic regions, it has been found for x=0.15 that the SC region is in rough correspondence to the region where Cu spins fluctuate fast beyond the mSR frequency window for both Zn- and Ni-substituted samples. According to the stripe model, it follows that, even for x = 0.15, the dynamical stripe correlations of spins and holes are pinned and localized around Zn and Ni, leading to the formation of the static stripe order and the suppression of superconductivity. These may indicate an importance of the dynamical stripe in the appearance of the high-Tc superconductivity in the hole-doped cuprates. In the overdoped regime of x=0.18 and 0.20, on the other hand, the SC region seems to be in rough correspondence to the region where Cu spins fluctuate fast beyond the mSR frequency window, though it appears that the Cu-spin dynamics and superconductivity are affected by the phase separation into SC and normal-state regions. Accepted Fri Sep 5, 2008 Tuning competing orders in La_{2-x}Sr_{x}CuO_{4} cuprate superconductors by the application of an external magnetic field J. Chang, Ch. Niedermayer, R. Gilardi, N. B. Christensen, H. M. Ronnow, D. F. McMorrow, Ay M., J. Stahn, O. Sobolev, A. Hiess, S. Pailhes, C. Baines, N. Momono, M. Oda, M. Ido and J. Mesot We report the results of a combined muon spin rotation and neutron scattering study on (LSCO) in the vicinity of the so-called 1/8-anomaly. Application of a magnetic field drives the system towards a magnetically ordered spin-density-wave state, which is fully developed at 1/8 doping. The results are discussed in terms of competition between antiferromagnetic and superconducting order parameters. Accepted Fri Sep 5, 2008
B. Huard, N. Stander, J. A. Sulpizio, and D. Goldhaber-Gordon We perform electrical transport measurements in graphene with several sample geometries. In particular, we design “invasive” probes crossing the whole graphene sheet as well as “external” probes connected through graphene side arms. The four-probe conductance measured between external probes... [Phys. Rev. B 78, 121402 ] Published Thu Sep 4, 2008 Read articleTakeshi Nishimatsu, Umesh V. Waghmare, Yoshiyuki Kawazoe, and David Vanderbilt A newly developed fast molecular dynamics method is applied to BaTiO3 ferroelectric thin-film capacitors with short-circuited electrodes or under applied voltage. The molecular dynamics simulations based on a first-principles effective Hamiltonian clarify that dead layers (or passive layers) betwe... [Phys. Rev. B 78, 104104 ] Published Thu Sep 4, 2008 Read articleK. Ziegler The appearance of long-range correlations near the Dirac point of a Dirac-type spinor model with random vector potential is studied. These correlations originate from a spontaneously broken symmetry and their corresponding Goldstone modes. Using a strong-disorder expansion, correlation functions and... [Phys. Rev. B 78, 125401 ] Published Tue Sep 2, 2008 Read articleHideaki Obuse, Akira Furusaki, Shinsei Ryu, and Christopher Mudry Static disorder in a noninteracting gas of electrons confined to two dimensions can drive a continuous quantum (Anderson) transition between a metallic and an insulating state when time-reversal symmetry is preserved but spin-rotation symmetry is broken. The critical exponent ν that characterizes... [Phys. Rev. B 78, 115301 ] Published Tue Sep 2, 2008 Read articleA. M. Kalashnikova, A. V. Kimel, R. V. Pisarev, V. N. Gridnev, P. A. Usachev, A. Kirilyuk, and Th. Rasing Coherent magnons and phonons are excited by subpicosecond laser pulses in the weak ferromagnet FeBO3 . Impulsive stimulated Raman scattering (ISRS) is proven to be the microscopic mechanism of the excitation. It is shown that coherent magnons can be excited by both linearly and circularly polarized... [Phys. Rev. B 78, 104301 ] Published Tue Sep 2, 2008 Read articleAndrey Chubukov and Ilya Eremin We explain the recently observed linear temperature dependence of the nodal Fermi velocity vF(T) in nearly optimally doped cuprates. We argue that it originates from electron-electron interaction and it is a fundamental property of an arbitrary two-dimensional (2D) Fermi liquid. We consider a spin... [Phys. Rev. B 78, 060509 ] Published Fri Aug 29, 2008 Read articleM. Debessai, J. J. Hamlin, and J. S. Schilling Whereas double hcp (dhcp) La superconducts at ambient pressure with Tc≃5 K , the other trivalent d -electron metals Sc, Y, and Lu only superconduct if high pressures are applied. Earlier measurements of the pressure dependence of Tc for Sc and Lu metal are here extended to much higher pressu... [Phys. Rev. B 78, 064519 ] Published Thu Aug 28, 2008 Read articleT. B. Tran, I. S. Beloborodov, Jingshi Hu, X. M. Lin, T. F. Rosenbaum, and H. M. Jaeger We investigate transport in weakly coupled metal nanoparticle arrays, focusing on the regime where tunneling is competing with strong single electron charging effects. This competition gives rise to an interplay between two types of charge transport. In sequential tunneling, transport is dominated b... [Phys. Rev. B 78, 075437 ] Published Tue Aug 26, 2008 Read articleD. N. Sheng, Olexei I. Motrunich, Simon Trebst, Emanuel Gull, and Matthew P. A. Fisher Developing a theoretical framework to access the quantum phases of itinerant bosons or fermions in two dimensions that exhibit singular structure along surfaces in momentum space but have no quasiparticle description remains a central challenge in the field of strongly correlated physics. In this pa... [Phys. Rev. B 78, 054520 ] Published Tue Aug 26, 2008 Read articleF. Pistolesi, Ya. M. Blanter, and Ivar Martin We study the model of a molecular switch comprised of a molecule with a soft vibrational degree of freedom coupled to metallic leads. In the presence of strong electron-ion interaction, different charge states of the molecule correspond to substantially different ionic configurations, which can lead... [Phys. Rev. B 78, 085127 ] Published Mon Aug 25, 2008 Read article |
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