Electron-Phonon Coupling Strength of Specific Phonons from First Principles Lapw Calculations

1988 ◽  
Vol 141 ◽  
Author(s):  
H. Krakauer ◽  
R. E. Cohen ◽  
W. E. Pickett
Keyword(s):  
Coupling Strength ◽  
First Principles ◽  
Mode Coupling ◽  
Local Density ◽  
Matrix Elements ◽  
Dual Representation ◽  
Electron Phonon Interaction ◽  
Electron Phonon Coupling ◽  
Coupling Strengths ◽  
The Difference

AbstractElectron-phonon matrix elements, phonon linewidths and mode coupling strengths are being calculated for La2-xMxCuO4 (M-divalent cation, for paramagnetic x-0.0 and for x-0.15 in a rigid band picture) from first principles local density calculations. The change in potential due to a particular phonon mode is calculated from the difference of self-consistent one-electron potentials, and appropriate Fermi surface averages are carried out for selected modes, allowing us to obtain the phonon linewidth due to the electron-phonon interaction, and the corresponding coupling strength λQ. Here we establish the numerical accuracy within the dual representation of the potential used in the Linearized Augmented Plane Wave (LAPW) method. Evaluations of phonon linewidths and mode coupling strengths are presented for Al and Nb and compared with previous information on these modes. We present preliminary results for the full matrix elements and coupling of the La2CuO4 oxygen planar X-point breathing mode, and compare with a simpler approximation.

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.

scholarly journals Evolution of high-frequency Raman modes and their doping dependence in twisted bilayer MoS2

Nanoscale ◽  
2020 ◽  
Vol 12 (33) ◽  
pp. 17272-17280 ◽  
Author(s):  
Rahul Debnath ◽  
Indrajit Maity ◽  
Rabindra Biswas ◽  
Varun Raghunathan ◽  
Manish Jain ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Coupling Strength ◽  
First Principles ◽  
High Frequency ◽  
Twist Angle ◽  
Interlayer Coupling ◽  
Phonon Coupling ◽  
Electron Phonon Coupling ◽  
Raman Modes ◽  
Systematic Evolution

Here, we demonstrate the systematic evolution of the interlayer coupling and electron-phonon coupling strength with twist angle in bilayer MoS2 using a combination of Raman spectroscopy and a combination of classical and first-principles based simulations.

scholarly journals Electron–phonon coupling in superconducting 1T-PdTe2

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Gloria Anemone ◽  
Pablo Casado Aguilar ◽  
Manuela Garnica ◽  
Fabian Calleja ◽  
Amjad Al Taleb ◽  
...  
Keyword(s):  
Acoustic Mode ◽  
Bcs Theory ◽  
Scanning Tunneling ◽  
Phonon Coupling ◽  
Tunneling Microscopy ◽  
Helium Atom Scattering ◽  
Electron Phonon Interaction ◽  
Electron Phonon Coupling ◽  
Topological States ◽  
The Difference

AbstractWe have determined the electron–phonon interaction in type II Dirac semimetallic 1T-PdTe2 by means of helium atom scattering. While 1T-PdTe2 is isostructural with 1T-PtTe2, only the former is superconductor. The difference can be traced to the substantially larger value of the electron–phonon coupling in 1T-PdTe2, λ = 0.58, obtained from the Debye-Waller attenuation of the He specular peak. With this value and the surface Debye temperature, ΘD = 106.2 K, we have figured out the superconducting critical temperature, Tc = 1.83 K given by the BCS theory, which is in good agreement with Tc = (1.95 ± 0.03) K obtained with low-temperature scanning tunneling microscopy. The value of the effective mass related to ΘD indicates that the large electron–phonon coupling in 1T-PdTe2 is due to coupling, not only with the zone-center optical mode O2 at 9.2 meV, as proposed in a recent theoretical study, but also with the zone-boundary acoustic mode LA. Our results suggest that the topological states of a Dirac cone play a negligible role on the onset of superconductivity.

Dynamical Jahn-Teller Systems: Internal Energy Resonance Structures of Isolated Jahn-Teller Molecules (E-b and T-t System)

1981 ◽  
Vol 36 (7) ◽  
pp. 685-693
Author(s):  
E. Sigmund ◽  
S. Brühl
Keyword(s):  
Phonon Coupling ◽  
Phonon Interaction ◽  
Resonance Structures ◽  
Energy Resonance ◽  
Electron Phonon Interaction ◽  
Transfer Processes ◽  
Electron Phonon Coupling ◽  
Jahn Teller ◽  
Coupling Strengths ◽  
T System

Abstract The internal energetic transfer processes of an E - b and T - t Jahn-Teller system are con­ sidered. The first system allows an exact description, whereas in the case of the second one ap­ proximations must be introduced in the region of intermediate electron-phonon coupling strengths. The occupation probabilities of the states of the uncoupled systems change with time by virtue of the electron-phonon interaction. The energies are directly related to these occupation probabilities. The resonant nature of the T - t system is reflected in the internal dynamics of the latter.

scholarly journals Electron-phonon interaction in In-induced √7 ×√3 structures on Si(111) from first-principles

2021 ◽  
Author(s):  
I. Yu. Sklyadneva ◽  
Rolf Heid ◽  
Pedro Miguel Echenique ◽  
Evgueni Chulkov
Keyword(s):  
Density Functional Theory ◽  
Double Layer ◽  
First Principles ◽  
Linear Response ◽  
Density Functional ◽  
Single Layer ◽  
Phonon Interaction ◽  
Functional Theory ◽  
Electron Phonon Interaction ◽  
The Density Functional Theory

Electron-phonon interaction in the Si(111)-supported rectangular √(7 ) ×√3 phases of In is investigated within the density-functional theory and linear-response. For both single-layer and double-layer √(7 ) ×√3 structures, it...

scholarly journals Dual subtractions

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Renato Maria Prisco ◽  
Francesco Tramontano
Keyword(s):  
Field Theory ◽  
Quantum Field ◽  
Matrix Elements ◽  
Leading Order ◽  
Initial State ◽  
Final State ◽  
Dual Representation ◽  
Subtraction Scheme ◽  
Theoretical Predictions ◽  
Perturbative Quantum

Abstract We propose a novel local subtraction scheme for the computation of Next-to-Leading Order contributions to theoretical predictions for scattering processes in perturbative Quantum Field Theory. With respect to well known schemes proposed since many years that build upon the analysis of the real radiation matrix elements, our construction starts from the loop diagrams and exploits their dual representation. Our scheme implements exact phase space factorization, handles final state as well as initial state singularities and is suitable for both massless and massive particles.

TRANSITION FREQUENCY OF STRONG-COUPLING IMPURITY BOUND POLARON IN AN ASYMMETRIC QUANTUM DOT

2012 ◽  
Vol 11 (03) ◽  
pp. 1250026 ◽  
Author(s):  
CHENG-SHUN WANG ◽  
YU-FANG CHEN ◽  
JING-JIN XIAO
Keyword(s):  
Excited State ◽  
Coupling Strength ◽  
State Energy ◽  
Transition Frequency ◽  
Phonon Coupling ◽  
Excited State Energy ◽  
Bound Polaron ◽  
Asymmetric Quantum Dot ◽  
Asymmetric Quantum ◽  
Electron Phonon Coupling

Properties of the excited state of strong-coupling impurity bound polaron in an asymmetric quantum dot are studied by using linear combination operator and unitary transformation methods. The first internal excited state energy, the excitation energy and the transition frequency between the first internal excited and the ground states of the impurity bound polaron as functions of the transverse and the longitudinal effective confinement lengths of the dot, the electron–phonon coupling strength and the Coulomb bound potential were derived. Our numerical results show that they will increase with decreasing the effective confinement lengths, due to interesting quantum size confining effects. But they are an increasing functions of the Coulomb bound potential. The first internal excited state energy is a decreasing function of the electron–phonon coupling strength whereas the transition frequency and the excitation energy are an increasing one of the electron–phonon coupling strength.

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.

MODIFICATION OF CASIMIR FORCES DUE TO BAND GAPS IN PERIODIC STRUCTURES

2002 ◽  
Vol 17 (06n07) ◽  
pp. 798-803 ◽  
Author(s):  
C. VILLARREAL ◽  
R. ESQUIVEL-SIRVENT ◽  
G. H. COCOLETZI
Keyword(s):  
Density Of States ◽  
Casimir Force ◽  
Periodic Structures ◽  
Local Density ◽  
Band Gaps ◽  
Basic Unit ◽  
Local Density Of States ◽  
Casimir Forces ◽  
Unit Cells ◽  
The Difference

The Casimir force between inhomogeneous slabs that exhibit a band-like structure is calculated. The slabs are made of basic unit cells each made of two layers of different materials. As the number of unit cells increases the Casimir force between the slabs changes, since the reflectivity develops a band-like structure characterized by frequency regions of high reflectivity. This is also evident in the difference of the local density of states between free and boundary distorted vacuum, that becomes maximum at frequencies corresponding to the band gaps. The calculations are restricted to vacuum modes with wave vectors perpendicular to the slabs.

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