LARGE POLARON IN AN ANHARMONIC CRYSTAL LATTICE

2009 ◽  
Vol 23 (01) ◽  
pp. 19-38 ◽  
Author(s):  
ADIL-GERAI KUSSOW
Keyword(s):  
Large Radius ◽  
Coupling Constant ◽  
Phonon Coupling ◽  
Anharmonic Crystal ◽  
Electron Phonon Interaction ◽  
Anharmonic Lattice ◽  
Longitudinal Phonon ◽  
Electron Phonon Coupling ◽  
Comparison Of The Results ◽  
Perovskite Type

Extending the Frohlich polaron problem to an anharmonic lattice, the author studies a polaronic state with a large radius of the wave function. The appropriate anharmonic part of the electron–phonon interaction Hamiltonian is derived, based on the methods of quantum field theory. Then, with the help of the perturbation theory, the anharmonic correction to the electron–phonon coupling constant is straightforwardly calculated. The estimate of this correction shows that the anharmonicity can considerably increase the e–ph coupling constant if the longitudinal phonon frequency is lower than ~10 meV. Several materials, molecular crystals α-sexithiophene (α-6T), α, ω dihexylsexithiophene (H-6T), and perovskite-type oxides, in which the anharmonic polaronic effects should be pronounced, are discussed. A comparison of the results with other anharmonic models of a polaronic state is drawn.

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.

The Estimate of the Electron–Phonon Coupling Constant in the Thin Film

1998 ◽  
Vol 12 (02) ◽  
pp. 177-189 ◽  
Author(s):  
M. Pantić ◽  
Lj. D. Mašković ◽  
B. S. Tošić
Keyword(s):  
Experimental Fact ◽  
Coupling Constant ◽  
Phonon Coupling ◽  
Metallic Films ◽  
Critical Temperatures ◽  
Dominant Form ◽  
Electron Phonon Interaction ◽  
Electron Phonon Coupling ◽  
Surface Electrons ◽  
Bulk Structures

Hamiltonians of electron–phonon interaction for thin metallic films are formulated. This is the basis for the estimate of the superconductivity critical temperature for films and corresponding bulk structures. It is shown that the interaction of surface electrons in the film with bulk phonons could explain the experimental fact that critical temperatures of the films are higher than the corresponding ones in bulk (massive) structures. Since above fact is valid nearly for all pure metallic, one can conclude that the dominant form or the interaction in films is the interaction of surface electrons with bulk phonons.

scholarly journals Translation-Invariant Excitons in a Phonon Field

2021 ◽  
Vol 6 (2) ◽  
pp. 20
Author(s):  
Victor D. Lakhno
Keyword(s):  
State Energy ◽  
Emission Spectra ◽  
Large Radius ◽  
Phonon Coupling ◽  
Translation Invariant ◽  
Phonon Field ◽  
Electron Phonon Interaction ◽  
Electron Phonon Coupling ◽  
Invariant Description ◽  
Nonzero Contribution

Large-radius excitons in polar crystals are considered. It is shown that translation invariant description of excitons interacting with a phonon field leads to a nonzero contribution of phonons into the exciton ground state energy only in the case of weak or intermediate electron-phonon coupling. A conclusion is made that self-trapped excitons cannot exist in the limit of strong coupling. Peculiarities of the absorption and emission spectra of translation invariant excitons in a phonon field are discussed. Conditions when the hydrogen-like exciton model remains valid in the case of electron-phonon interaction are found.

scholarly journals Estimation of electron-phonon coupling constant in Ba1-xKxBiO3

2020 ◽  
Vol 1686 ◽  
pp. 012049
Author(s):  
Alexander E Lukyanov ◽  
Vyacheslav D Neverov ◽  
Andrey V Krasavin ◽  
Alexey P Menushenkov
Keyword(s):  
Coupling Constant ◽  
Phonon Coupling ◽  
Electron Phonon Coupling

PATH-INTEGRAL APPROACH FOR ELECTRON–PHONON INTERACTION EFFECTS IN HARMONIC QUANTUM DOTS

1996 ◽  
Vol 10 (22) ◽  
pp. 2781-2796 ◽  
Author(s):  
SOMA MUKHOPADHYAY ◽  
ASHOK CHATTERJEE
Keyword(s):  
Quantum Dots ◽  
Path Integral ◽  
State Energy ◽  
Coupling Parameter ◽  
Three Dimensions ◽  
Integral Approach ◽  
Phonon Coupling ◽  
Electron Phonon Interaction ◽  
Electron Phonon Coupling ◽  
Parabolic Confinement

We use the Feynman–Haken path-integral formalism to obtain the polaronic correction to the ground state energy of an electron in a polar semiconductor quantum dot with parabolic confinement in both two and three dimensions. We perform calculations for the entire range of the electron–phonon coupling parameter and for arbitrary confinement length. We apply our results to several semiconductor quantum dots and show that the polaronic effect in some of these dots can be considerably large if the dot sizes are made smaller than a few nanometers.

scholarly journals Charge order lock-in by electron-phonon coupling in La1.675Eu0.2Sr0.125CuO4

2021 ◽  
Vol 7 (27) ◽  
pp. eabg7394
Author(s):  
Qisi Wang ◽  
Karin von Arx ◽  
Masafumi Horio ◽  
Deepak John Mukkattukavil ◽  
Julia Küspert ◽  
...  
Keyword(s):  
Wave Vector ◽  
Charge Order ◽  
Charge Ordering ◽  
Electron Interaction ◽  
Phonon Coupling ◽  
Electron Phonon Interaction ◽  
Self Energy ◽  
Electron Phonon Coupling ◽  
Charge Stripe ◽  
Lock In

Charge order is universal to all hole-doped cuprates. Yet, the driving interactions remain an unsolved problem. Electron-electron interaction is widely believed to be essential, whereas the role of electron-phonon interaction is unclear. We report an ultrahigh-resolution resonant inelastic x-ray scattering (RIXS) study of the in-plane bond-stretching phonon mode in stripe-ordered cuprate La1.675Eu0.2Sr0.125CuO4. Phonon softening and lifetime shortening are found around the charge ordering wave vector. In addition to these self-energy effects, the electron-phonon coupling is probed by its proportionality to the RIXS cross section. We find an enhancement of the electron-phonon coupling around the charge-stripe ordering wave vector upon cooling into the low-temperature tetragonal structure phase. These results suggest that, in addition to electronic correlations, electron-phonon coupling contributes substantially to the emergence of long-range charge-stripe order in cuprates.

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