Evaluation of the electron-phonon interaction and transition temperature in the oxide superconductors

1989 ◽  
Vol 2 (2) ◽  
pp. 317-321 ◽  
Author(s):  
D. A. Papaconstantopoulos
Keyword(s):  
Transition Temperature ◽  
Oxide Superconductors ◽  
Phonon Interaction ◽  
Electron Phonon Interaction

ELECTRON-PHONON INTERACTION AND SUPERCONDUCTIVITY IN OXIDE SUPERCONDUCTORS La2−xSrxCuO4

1993 ◽  
Vol 07 (01n03) ◽  
pp. 182-185
Author(s):  
M. SHIRAI ◽  
T. KINOSHITA ◽  
K. MOTIZUKI
Keyword(s):  
Tight Binding ◽  
Wide Energy Range ◽  
Oxide Superconductors ◽  
Tunneling Conductance ◽  
Eliashberg Equations ◽  
Phonon Modes ◽  
Phonon Interaction ◽  
Characteristic Structure ◽  
Electron Phonon Interaction ◽  
Wide Energy

Effects of electron-phonon interaction on lattice dynamics in oxide superconductors La 2−x Sr x CuO 4 (LSC) are studied microscopically on the basis of the tight-binding band fitted to the first principle band. Breathing-type vibrations of oxygen atoms in the CuO 2 plane are renormalized significantly at around (π/a, π/a, 0) and (π/a, 0, 0) due to strong dependences of the electron-phonon interaction on wavevectors and phonon modes. In the framework of the usual phonon-mediated pairing mechanism, superconducting properties, such as transition temperatures and tunneling spectra, are studied by solving isotropic Eliashberg equations. The spectral function α2F(ω) has a characteristic structure over a wide energy range below 85 meV. The tunneling conductance d I/ d V and its derivative d 2I/ d V2 calculated have prominent peaks below 40 meV, which show good correspondences to those observed by recent tunneling experiments.

ELECTRON-PHONON INTERACTION, LATTICE DYNAMICS AND SUPERCONDUCTIVITY OF LAYERED TRANSITION-METAL DICHALCOGENIDE NbS2

1993 ◽  
Vol 07 (01n03) ◽  
pp. 188-192 ◽  
Author(s):  
Yoshimasa NISHIO ◽  
Masafumi SHIRAI ◽  
Naoshi SUZUKI ◽  
Kazuko MOTIZUKI
Keyword(s):  
Transition Temperature ◽  
Lattice Dynamics ◽  
Tight Binding ◽  
Transition Metal Dichalcogenide ◽  
Superconducting Transition ◽  
Lattice Instability ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Order Of Magnitude ◽  
Layered Transition Metal

Lattice dynamics of NbX 2( X = S , Se ) is studied by taking account of electron-phonon interaction derived microscopically on the basis of the realistic tight-binding bands fitted to the first-principle bands of NbX 2. Remarkable frequency renormalization of Σ1 phonon mode around [Formula: see text] is caused due to characteristic wave-vector and mode dependences of the electron-phonon interaction as well as nesting effect of Fermi surface. It is also shown that the short range force constant for neighboring X ions on different X-layers in the same X-Nb-X sandwich determines primarily whether lattice instability occurs ( NbSe 2 case) or does not occur ( NbS 2 case). By using the electron-phonon interaction and the lattice dynamics obtained for NbS 2 we have calculated the spectral function α2F(ω) and determined superconducting transition temperature T c by solving the linearlized Eliashberg equation. Renormalization of phonon frequencies due to the eletron-phonon interaction raises considerably the transition temperature and the obtained value of T c agrees in order of magnitude with the experimental data.

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