Peculiarities of the Electron-Phonon Interaction in Graphite Containing Metallic Intercalated Layers

2010 ◽  
Vol 297-301 ◽  
pp. 75-81 ◽  
Author(s):  
Alexander Feher ◽  
S.B. Feodosyev ◽  
I.A. Gospodarev ◽  
V.I. Grishaev ◽  
K.V. Kravchenko ◽  
...  
Keyword(s):  
Jacobi Matrix ◽  
Local Density ◽  
Dynamic Properties ◽  
Electronic States ◽  
Bcs Theory ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Density Of Electronic States ◽  
Eliashberg Equation ◽  
Phonon Spectra

The calculation of the local density of electronic states of graphene with vacancies, using the method of Jacobi matrix, was performed. It was shown that for atoms in the sublattice with a vacancy the local density of electronic states conserves the Dirac singularity, similarly as in an ideal graphene. A quasi-Dirac singularity was observed also in the phonon spectra of graphite for the atom displacements in the direction perpendicular to layers. Changes of phonon spectra of graphite intercalated with various metals were analyzed. On the basis of our results and using the BCS theory and Eliashberg equation we proposed what dynamic properties an intercalated graphite system should show to obtain an increased Tc.

Electron Tunneling in High Tc Superconductors

MRS Bulletin ◽  
1990 ◽  
Vol 15 (6) ◽  
pp. 44-49 ◽  
Author(s):  
J.M. Valles ◽  
R.C. Dynes
Keyword(s):  
Energy Gap ◽  
Electron Tunneling ◽  
Quantitative Description ◽  
Bcs Theory ◽  
Phonon Interaction ◽  
Microscopic Mechanism ◽  
Electron Phonon Interaction ◽  
Current Voltage ◽  
Superconducting Energy Gap ◽  
Electron Phonon Coupling

Electron tunneling measurements have proven enormously valuable in studies of conventional superconductors. Very early measurements confirmed, in an especially convincing way, the existence of the superconducting energy gap, and more detailed studies demonstrated the spectral form of the gap and its temperature dependence. These measurements were instrumental in confirming in some detail the predictions of the Bardeen, Cooper, Schrieffer (BCS) theory of superconductivity in simple metals. For example, it was shown very clearly that the ratio of the energy gap (2Δ) and critical temperature Tc was close to the BCS value (2Δ/kTc = 3.5). As the sophistication of the technique improved, deviations from this BCS weak coupling limit became apparent (2Δ/kTc was measured to be >4 in materials like Pb, for example), and subtle structure in the current-voltage characteristics of tunnel junctions unearthed a signature of the electron-phonon interaction—the microscopic mechanism responsible for superconductivity in these traditional materials. Through a quantitative analysis of this structure, people were able to extract a function α2(ω)F(ω), which is the phonon density of states F(ω) modulated by the electron-phonon coupling function α2(ω). This function gave a quantitative description of the electron-phonon interaction and confirmed beyond a doubt that the electron-phonon interaction was responsible for superconductivity.

THE TEMPERATURE DEPENDENCE OF THE ENERGY LEVELS OF SHALLOW DONOR IMPURITIES IN SILICON

1967 ◽  
Vol 45 (4) ◽  
pp. 1421-1438 ◽  
Author(s):  
C. Y. Cheung ◽  
Robert Barrie
Keyword(s):  
Temperature Dependence ◽  
Energy Levels ◽  
Electronic States ◽  
Shallow Donor ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Doped Silicon ◽  
Phosphorus Doped

A calculation is made of the temperature dependence of the energy levels of shallow donor impurities in silicon. This temperature dependence arises from the electron–phonon interaction and we consider mixing only of the {1s}, {2s), and {2p0} electronic states. A comparison is made with experiment for the case of phosphorus-doped silicon.

scholarly journals Effect of electron-phonon interaction on the formation of one-dimensional electronic states in coupled Cl vacancies

2015 ◽  
Vol 91 (23) ◽  
Author(s):  
Bruno Schuler ◽  
Mats Persson ◽  
Sami Paavilainen ◽  
Niko Pavliček ◽  
Leo Gross ◽  
...  
Keyword(s):  
Electronic States ◽  
Phonon Interaction ◽  
One Dimensional ◽  
Electron Phonon Interaction

ELECTRON-PHONON INTERACTION IN TERNARY SILICIDES MGaSi (M=Ca, SrandBa)

2005 ◽  
Vol 19 (01n03) ◽  
pp. 163-165
Author(s):  
G. Q. HUANG ◽  
L. F. CHEN
Keyword(s):  
Density Functional ◽  
Striking Feature ◽  
Full Potential ◽  
Superconducting Transition ◽  
Phonon Coupling ◽  
Potential Density ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Phonon Spectra ◽  
Electron Phonon Coupling

The electron-phonon (EP) interaction in ternary silicides M GaSi with M= Ca , Sr and Ba are calculated using the full potential, density-functional-based method. A striking feature of the phonon spectra is the existence of very soft " B 1g" mode, which is strong anharmonic and plays an important role in superconductivity of the M GaSi compounds. The superconducting transition temperatures Tc in these compounds have been evaluated. It is found that the variation trend in Tc can be explained from the strength of the electron-phonon coupling.

The Gap Function in YBa2Cu3O7

1998 ◽  
Vol 12 (29n31) ◽  
pp. 3057-3062 ◽  
Author(s):  
G. L. Zhao ◽  
D. Bagayoko
Keyword(s):  
Electronic Structure ◽  
Transition Temperature ◽  
Energy Gap ◽  
Electronic States ◽  
Gap Function ◽  
Interaction Matrix ◽  
Matrix Elements ◽  
Phonon Interaction ◽  
Gap Equation ◽  
Electron Phonon Interaction

We have solved the four-dimensional anisotropic Eliashberg gap equation for YBa2Cu3O7 (YBCO) using the calculated electronic structure and the electron–phonon interaction matrix elements. The calculated T c for YBCO is about 89 K or μ*= 0.1. At or slightly above the transition temperature T c , the real part of the gap function Δ(k, 0), for all the k-points on the Fermi surface, becomes zero and the material is not superconducting. However, the energy gap function Δ(k,ω) is still nonzero for ω > 0 for some electronic states, leading to a pseudo-gap behavior in YBCO.

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