ELECTRONIC STRUCTURE AND ELECTRON-PHONON INTERACTION FOR La2-xMxCuO4 SYSTEMS

1987 ◽  
Vol 01 (03n04) ◽  
pp. 951-955 ◽  
Author(s):  
A.A. Aligia ◽  
K.H. Bennemann ◽  
M. Kulić ◽  
V. Zlatić
Keyword(s):  
Electronic Structure ◽  
Tight Binding ◽  
Relative Importance ◽  
Binding Theory ◽  
Phonon Coupling ◽  
Phonon Modes ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Electron Phonon Coupling

The electronic properties and the electron-phonon coupling in La2-xMxCuO4 type compounds are studied within the tight-binding theory. Derived expressions for electron-phonon coupling exhibit clearly the relative importance of various phonon modes. The possible role of the breathing type oxygen vibrations in the electronically driven lattice instabilities and superconductivity is discussed as a function of the impurity concentration.

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.

INFLUENCE OF ELECTRON–PHONON INTERACTION ON EFFECTIVE MASS IN SOME HEAVY FERMION (HF) SYSTEMS

2008 ◽  
Vol 22 (04) ◽  
pp. 365-379 ◽  
Author(s):  
S. MOHANTY ◽  
B. K. KALTA ◽  
P. NAYAK
Keyword(s):  
Effective Mass ◽  
Coupling Strength ◽  
Heavy Fermion ◽  
Simple Expression ◽  
Model Parameters ◽  
Coupling Mechanism ◽  
Phonon Coupling ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Electron Phonon Coupling

It is a fact that for ordinary metals, the electron–phonon interaction increases the quasi-particle mass, which is in contrast to the finding by Fulde et al. that, for some heavy Fermion (HF) systems, it decreases. Some experiments on HF systems suggest that there exists a strong coupling of the elastic degrees of freedom with these at the electronic and magnetic ones. To understand the effect of electron–phonon interaction on effective mass, the electron–phonon coupling mechanism in the framework of the periodic Anderson model is considered, and a simple expression is derived. This involves various model parameters namely, the position of the 4f level; the effective coupling strength, g, temperature, b; and the electron–phonon coupling strength, r. The influence of these parameters on the value of effective mass is studied, and interesting results were found. For simplicity, the numerical calculation is performed in the long wavelength limit.

EFFECTS OF ELECTRON–PHONON INTERACTION IN TUNNELING PROCESSES IN NANOSTRUCTURES

2007 ◽  
Vol 06 (05) ◽  
pp. 411-414
Author(s):  
P. I. ARSEYEV ◽  
N. S. MASLOVA
Keyword(s):  
Phonon Coupling ◽  
Phonon Interaction ◽  
Strong Electron ◽  
Resonant Case ◽  
Electron Phonon Interaction ◽  
Electron Phonon Coupling ◽  
Tunneling Conductivity ◽  
Nonequilibrium Effects ◽  
Inelastic Tunneling

Tunneling through a system with two discrete electron levels coupled by electron–phonon interaction is considered. The interplay between elastic and inelastic tunneling channels is analyzed for a strong electron–phonon coupling in the resonant case. It is shown that the intensity and the width of peaks in tunneling conductivity are strongly influenced by nonequilibrium effects.

Velocity renormalization in graphene: The role of trigonal warping and electron–phonon coupling effects

2017 ◽  
Vol 31 (30) ◽  
pp. 1750235 ◽  
Author(s):  
B. S. Kandemir ◽  
N. Gökçek
Keyword(s):  
Analytical Solution ◽  
Fermi Velocity ◽  
Combined Effects ◽  
Phonon Coupling ◽  
Strong Anisotropy ◽  
Energy Bands ◽  
Phonon Modes ◽  
Electron Phonon Coupling ◽  
Trigonal Warping

We investigate the combined effects of trigonal warping and electron–phonon interactions on the renormalization of the Fermi velocity in graphene. We present an analytical solution to the associated Fröhlich Hamiltonian describing the interaction of doubly degenerate-optical phonon modes of graphene with electrons in the presence of trigonal warp within the framework of Lee–Low–Pines theory. On the basis of our model, it is analytically shown that in addition to its renormalization, Fermi velocity exhibits strong anisotropy due to the trigonal warping. It is also found that in the regime where the trigonal warp starts, distortion of energy bands emerges due to electron–phonon coupling, and the bands exhibit strong anisotropy.

Investigations of the Thermal Shifts and Electron–Phonon Coupling Parameters of R1 and R2 Lines for Cr3+-doped Forsterite

2014 ◽  
Vol 69 (8-9) ◽  
pp. 497-500 ◽  
Author(s):  
Xiao-Xuan Wu ◽  
Wen-Chen Zheng
Keyword(s):  
Thermal Expansion ◽  
Spectral Lines ◽  
Coupling Coefficients ◽  
Phonon Coupling ◽  
Lattice Thermal Expansion ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Electron Phonon Coupling ◽  
Coupling Parameters ◽  
Vibrational Contribution

The thermal shifts of R1 and R2 lines in Cr3+-doped forsterite (Mg2SiO4) are studied by considering both the static contribution due to lattice thermal expansion and the vibrational contribution due to electron-phonon interaction. In the studies, the thermal expansion coefficient of the Cr3+ center is assumed reasonably as that of the corresponding cluster in the host crystal. The results suggest that for R1 and R2 lines the static contributions are opposite in sign and in magnitude about 37% and 45%, respectively, of the corresponding vibrational contributions. The true electron-phonon coupling coefficients α' (obtained by considering both contributions) increase by about 58% and 81%, respectively, for R1 and R2 lines in comparison with the corresponding parameters α obtained by considering only the vibrational contribution. It appears that for the reasonable explanation of thermal shift of spectral lines and the exact estimation of electron-phonon coupling coefficient, both the static and vibrational contributions should be taken into account

ELASTIC PROPERTIES OF THE Zn SUBSTITUTED ErBa2Cu3O7-δ SUPERCONDUCTOR

2003 ◽  
Vol 17 (02) ◽  
pp. 75-82
Author(s):  
T. V. CHONG ◽  
R. ABD-SHUKOR
Keyword(s):  
Longitudinal Velocity ◽  
Shear Velocity ◽  
Spin Correlation ◽  
Coupling Constant ◽  
Phonon Coupling ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Electron Phonon Coupling ◽  
Overlap Method ◽  
Pulse Echo

Ultrasonic longitudinal and shear velocity in superconducting ErBa 2( Cu 3-x Zn x) O 7-δ (x = 0, 0.01 and 0.05) have been measured using the pulse-echo-overlap method at frequency 5–10 MHz in the temperature range 80–300 K. Longitudinal velocity hysteresis and elastic anomaly were observed in the x = 0 sample. Similar hysteresis was not observed in the x = 0.01 and 0.05 samples. The characteristic Debye temperature and electron–phonon coupling constant were calculated. The absence of hysteresis for longitudinal velocity in the x = 0.01 and 0.05 samples may be due to the spin correlation at the CuO 2 planes which affects the electron–phonon interaction.

scholarly journals Impact of electron–phonon coupling on electron transport through T-shaped arrangements of quantum dots in the Kondo regime

2021 ◽  
Vol 12 ◽  
pp. 1209-1225
Author(s):  
Patryk Florków ◽  
Stanisław Lipiński
Keyword(s):  
Quantum Dots ◽  
Mean Field ◽  
Strongly Correlated ◽  
Interference Effects ◽  
Phonon Coupling ◽  
Many Body ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Kondo Effects ◽  
Electron Phonon Coupling

We calculate the conductance through strongly correlated T-shaped molecular or quantum dot systems under the influence of phonons. The system is modelled by the extended Anderson–Holstein Hamiltonian. The finite-U mean-field slave boson approach is used to study many-body effects. Phonons influence both interference and correlations. Depending on the dot unperturbed energy and the strength of electron–phonon interaction, the system is occupied by a different number of electrons that effectively interact with each other repulsively or attractively. This leads, together with the interference effects, to different spin or charge Fano–Kondo effects.

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.

DISPERSION OF INTERFACE OPTICAL PHONONS AND THEIR COUPLING WITH ELECTRONS IN ASYMMETRICAL WURTZITEGaN/Ga1-xAlxNQUANTUM WELLS

2005 ◽  
Vol 12 (03) ◽  
pp. 433-442
Author(s):  
LI ZHANG ◽  
SONG GAO ◽  
JUN-JIE SHI
Keyword(s):  
Frequency Dispersion ◽  
Uniaxial Crystal ◽  
Phonon Modes ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Electron Phonon Coupling ◽  
Crystal Model ◽  
Physical Reasons ◽  
Dielectric Continuum ◽  
Dielectric Continuum Model

Within the framework of the dielectric continuum model and Loudon's uniaxial crystal model, the properties of frequency dispersion of the interface optical (IO) phonon modes and the coupling functions of electron–IO-phonon interaction in an asymmetrical wurtzite quantum well (QW) are deduced and analyzed via the method of electrostatic potential expansion. Numerical results reveal that in general, there are four branches of IO phonon modes in the systems. The dispersions of the four branches of IO phonon modes are obvious only when the free wavenumber ktin xy plane is small. The degenerating behavior of all the four branches of IO phonon modes in the asymmetric wurtzite QWs has been clearly observed for small kt. When ktis relatively large, with the increase of kt, the frequencies of the IO phonon modes converge to the four definite limiting frequencies in the corresponding wurtzite single planar heterostructure. This feature is obviously different from that in symmetric wurtzite QW, and the mathematical and physical reasons have been analyzed in depth. The calculations of electron–phonon coupling function show that the electrostatic distribution of the IO modes is neither symmetrical nor antisymmetrical, and the high-frequency IO phonon branches and the short-wavelength IO phonon modes play a more important role in the electron–phonon interaction.

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