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We compute the electronic structure, momentum resolved spectral function and optical conductivity of the new superconductor LaO$_{1-x}$F$_x$FeAs within the combination of the Density functional theory and the Dynamical Mean Field Theory. We…

Strongly Correlated Electrons · Physics 2009-11-13 K. Haule , J. H. Shim , G. Kotliar

We present a first principles investigation of the lattice dynamics and electron-phonon coupling of the high-T_c superconductor YBa_2Cu_3O_7 within the framework of density functional perturbation theory using a mixed-basis pseudopotential…

Superconductivity · Physics 2009-11-07 K. -P. Bohnen , R. Heid , M. Krauss

Inelastic neutron scattering studies have been carried out on selected phonons and magnetic excitations of a crystal of superconducting (SC) Ca$_{10}$Pt$_4$As$_8$(Fe$_{1-x}$Pt$_x$As)$_{10}$ with the onset transition temperature $T_{\rm…

We analyze the effects of an electron-phonon interaction on the one-electron spectral weight A(k,omega) of a d_{x^2-y^2} superconductor. We study the case of an Einstein phonon mode with various momentum-dependent electron-phonon couplings…

Superconductivity · Physics 2009-11-10 A. W. Sandvik , D. J. Scalapino , N. E. Bickers

The effect of the 16O-->18O substitution on the superconducting transition temperatures Tc of NaxCoO2.yH2O has been studied for several sets of samples. Each set has two kinds of samples, one with the oxygen sites in the CoO2 layers filled…

Superconductivity · Physics 2008-04-14 Mai Yokoi , Yoshiaki Kobayashi , Masatoshi Sato , Shunji Sugai

We perform analysis of the band structure, phonon dispersion, and electron-phonon interactions in three types of small-radius carbon nanotubes. We find that the (5,5) can be described well by the zone-folding method and the electron-phonon…

Superconductivity · Physics 2009-11-10 Ryan Barnett , Eugene Demler , Efthimios Kaxiras

The planar oxygen isotope effect coefficient measured as a function of hole doping in the Pr- and La-doped YBa2Cu3O7 (YBCO) and the Ni-doped La1.85Sr0.15CuO4 (LSCO) superconductors quantitatively and qualitatively follows the form…

Superconductivity · Physics 2017-11-22 S. Weyeneth

Ferromagnetism was recently observed at unexpectedly high temperatures in La-doped CaB_6. The starting point of all theoretical proposals to explain this observation is a semimetallic electronic structure calculated for CaB_6 within the…

Condensed Matter · Physics 2016-08-31 H. J. Tromp , P. van Gelderen , P. J. Kelly , G. Brocks , P. A. Bobbert

We present a combined density-functional-perturbation-theory and inelastic neutron scattering study of the lattice dynamical properties of YNi2B2C. In general, very good agreement was found between theory and experiment for both phonon…

Superconductivity · Physics 2015-06-19 F. Weber , L. Pintschovius , W. Reichardt , R. Heid , K. -P. Bohnen , A. Kreyssig , D. Reznik , K. Hradil

Coupling among conduction electrons (e.g. Zhang-Rice singlet) are often manifested in the core level spectra of exotic materials such as cuprate superconductors, manganites, etc. These states are believed to play key roles in the ground…

We report a detailed first-principles study of the structural, electronic and vibrational properties of the superconducting C$_{32}$ phase of the ternary alloy CaAl$_{2-x}$Si$_x$, both in the experimental range $0.6 \leq x \leq 1.2$, for…

Superconductivity · Physics 2009-11-11 Matteo Giantomassi , Lilia Boeri , Giovanni B. Bachelet

Chemical doping has recently become a very important strategy to induce superconductivity especially in complex compounds. Distinguished examples include Ba-doped La$_2$CuO$_4$ (the first high temperature superconductor), K-doped BaBiO$_3$,…

Superconductivity · Physics 2009-02-22 Guanghan Cao , Cao Wang , Zengwei Zhu , Shuai Jiang , Yongkang Luo , Shun Chi Zhi Ren , Qian Tao , Yuetao Wang , Zhu'an Xu

We measured the resistivity, diamagnetization, and low-temperature specific heat of the newly discovered noncentrosymmetric superconductor Mg_(12-delta)Ir_19B_16. The temperature dependence of specific heat is consistent with the model of…

Superconductivity · Physics 2007-08-28 Gang Mu , Yue Wang , Lei Shan , Hai-Hu Wen

We investigate the behavior of phonons at the epitaxial interface between YBa2Cu3O7-{\delta} thin film and (La,Sr)(Al,Ta)O3 substrate using vibrational electron energy loss spectroscopy. Interfacial phonon modes with different degrees of…

The discovery of a new beta-pyrochlore oxide superconductor CsOs2O6 with Tc = 3.3 K is reported. It is the third superconductor in the family of beta-pyrochlore oxides, following KOs2O6 with Tc = 9.6 K and RbOs2O6 with Tc = 6.3 K. The Tc of…

Superconductivity · Physics 2009-11-10 Shigeki Yonezawa , Yuji Muraoka , Zenji Hiroi

Monolayer Mo$_2$C is a new member of two-dimensional materials. Here the electronic structure and lattice dynamics of monolayer Mo$_2$C are calculated. According to the electron-phonon interaction, it is predicted that monolayer Mo$_2$C…

Mesoscale and Nanoscale Physics · Physics 2017-01-24 Jun-Jie Zhang , Shuai Dong

The parent compounds of the copper oxide high-Tc superconductors are unusual insulators. Superconductivity arises when they are properly doped away from stoichiometry1. In Bi2Sr2CaCu2O8+x, superconductivity results from doping with excess…

The exact formula of Tc's equation and the isotope effect exponent of two-band s-wave superconductors in weak-coupling limit are derived by considering the influence of two kinds of density of state : constant and van Hove singularity. The…

Superconductivity · Physics 2009-11-11 P. Udomsamuthirun , C. Kumvongsa , A. Burakorn , P. Changkanart , S. Yoksan

We report the superconductivity at above 30 K in a new FeSe-layer compound K0.8Fe2Se2 (nominal composition) achieved by metal K intercalating in between FeSe layers. It is isostructural to BaFe2As2 and possesses the highest Tc for…

Superconductivity · Physics 2019-06-12 Jiangang Guo , Shifeng Jin , Gang Wang , Shunchong Wang , Kaixing Zhu , Tingting Zhou , Meng He , Xiaolong Chen

In Fe-As based superconductors magnetism and superconductivity show strong sensitivity to the lattice, suggesting a possibility of unconventional electron-phonon coupling. We investigated c-axis polarized phonons in doped and undoped…