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.

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.

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.

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.

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.

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.

THE INFLUENCE OF ELECTRIC FIELD ON THE GROUND-STATE LIFETIME OF POLARON IN A PARABOLIC QUANTUM DOT

2011 ◽  
Vol 25 (03) ◽  
pp. 203-210
Author(s):  
WEI-PING LI ◽  
JI-WEN YIN ◽  
YI-FU YU ◽  
JING-LIN XIAO
Keyword(s):  
Quantum Dot ◽  
Electric Field ◽  
Ground State Energy ◽  
Ground State ◽  
State Energy ◽  
Phonon Coupling ◽  
Phonon Interaction ◽  
Strong Electron ◽  
Electron Phonon Interaction ◽  
Parabolic Quantum Dot

The ground-state energy of polaron was obtained with strong electron-LO-phonon coupling by using a variational method of the Pekar type in a parabolic quantum dot (QD). Quantum transition occurs in the quantum system due to the electron-phonon interaction and the influence of temperature. That is the polaron transition from the ground-state to the first-excited state after absorbing a LO-phonon and it causes the changing of the polaron lifetime. Numerical calculations are performed and the results illustrate the relations of the ground-state lifetime of the polaron on the ground-state energy of polaron, the electric field strength, the temperature, the electron-LO-phonon coupling strength and the confinement length of the quantum dot.

Three-Spin-Polarons and Their Elastic Interaction in Cuprates

2003 ◽  
Vol 17 (10n12) ◽  
pp. 415-421 ◽  
Author(s):  
B. I. Kochelaev ◽  
A. M. Safina ◽  
A. Shengelaya ◽  
H. Keller ◽  
K. A. Müller ◽  
...  
Keyword(s):  
Phase Separation ◽  
Ground State ◽  
State Energy ◽  
Elastic Interaction ◽  
Wave Functions ◽  
Extended Hubbard Model ◽  
Phonon Coupling ◽  
Phonon Field ◽  
Oxygen Hole ◽  
Spin Polarons

Properties of quasiparticles in doped cuprates formed by an oxygen hole and two adjacent copper holes are investigated on the basis of the extended Hubbard model. The ground state energy, wave functions and the polaron-phonon coupling are calculated. We also analyzed the polaron-polaron interaction via the phonon field. It was found that this interaction is highly anisotropic and can explain the experimentally observed phase separation in the strongly underdoped LaSrCuO:Mn system.

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.

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