Bound polaron in a narrow-band polar crystal

1993 ◽  
Vol 71 (11-12) ◽  
pp. 493-500
Author(s):  
Y. Lépine ◽  
O. Schönborn
Keyword(s):  
Effective Mass ◽  
Ground State ◽  
Narrow Band ◽  
Wave Functions ◽  
Phonon Coupling ◽  
Polar Crystal ◽  
Bound Polaron ◽  
Narrow Bandwidth ◽  
Electron Phonon Coupling ◽  
Shallow Impurities

The ground-state energy of a bound polaron in a narrow-band polar crystal (such as a metal oxide) is studied using variational wave functions. We use a Fröhlich-type Hamiltonian on which the effective mass approximation has not been effected and in which a Debye cutoff is made on the phonon wave vectors. The wave functions that are used are general enough to allow the existence of a band state and of a self-trapped state and are reliable in the nonadiabatic limit. We find that three ground states are possible for this system. First, for small electron–phonon coupling, moderate bandwidth, and shallow impurities, the usual effective-mass hydrogenic ground state is found. For a narrow bandwidth and a deep defect, a collapsed state is predicted in which the polaron coincides with the position of the defect. Finally, for moderate electron–phonon coupling, narrow bandwidth, and a very weak defect, a self-trapped polaron in a hydrogenic state is predicted. Our conclusions are presented as asymptotic expansions and as phase diagrams indicating the values of the parameters for which each phase can be found.

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.

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.

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.

LATTICE DYNAMICS AND ANYON SUPERCONDUCTORS

1990 ◽  
Vol 04 (18) ◽  
pp. 1143-1151 ◽  
Author(s):  
D.M. GAITONDE ◽  
SUMATHI RAO
Keyword(s):  
Magnetic Field ◽  
Gauge Field ◽  
Spectral Function ◽  
Carrier Concentration ◽  
Ground State ◽  
Lattice Dynamics ◽  
Phonon Coupling ◽  
Dominant Effect ◽  
Electron Phonon Coupling ◽  
New Type

We consider a model of anyons—fermions coupled to a statistical gauge field—also coupled to phonons via the usual electron-phonon coupling. We study the phonon response when the system is in the superconducting anyon ground state and show the existence of peaks in the phonon spectral function whose frequencies shift with carrier concentration. We suggest that when the electron-phonon coupling is the dominant effect, there could arise a new type of BCS ground state with a spontaneously generated P and T violating supercurrent, that expels the statistical magnetic field.

Interchain Alignments and Ground State in Organic Ferromagnets

1998 ◽  
Vol 12 (28) ◽  
pp. 1167-1174
Author(s):  
W. Z. Wang ◽  
K. L. Yao ◽  
H. Q. Lin
Keyword(s):  
Spin Density ◽  
Ground State ◽  
Main Chain ◽  
Phonon Coupling ◽  
Structure Transition ◽  
Interchain Coupling ◽  
Ferromagnetic Structure ◽  
Phase Alignment ◽  
Electron Phonon Coupling ◽  
Organic Ferromagnets

Two kinds of alignments of two neighboring π-conjugated organic ferromagnetic chains are studied by considering the itinerary of electrons, electron–phonon coupling, the Hubbard repulsion and the interchain coupling. It is shown that the out-of-phase alignment is a more stable ferromagnetic structure than in-phase alignment. For out-of-phase alignment, there is a structure transition at a critical interchain coupling, at which the dimerizations of two chains have the same size and reverse sign. Interchain coupling results in transfer of spin density between each main chain and the side radicals.

SELF-TRAPPING TRANSITION OF ACOUSTIC POLARON IN SLAB

2013 ◽  
Vol 27 (08) ◽  
pp. 1350050
Author(s):  
JUNHUA HOU ◽  
XIAOMING DONG ◽  
XIAOFENG DUAN
Keyword(s):  
Ground State Energy ◽  
Ground State ◽  
State Energy ◽  
Alkali Halides ◽  
2D Systems ◽  
Phonon Coupling ◽  
Length Unit ◽  
First Derivative ◽  
Electron Phonon Coupling ◽  
Self Trapping

Self-trapping transition of the acoustic polaron in slab is researched by calculating the polaron ground state energy and the first derivative of the ground state energy with respect to the electron–phonon coupling. It is indicated that the possibility of self-trapping transition for acoustic polaron in slab fall in between 3D and 2D systems. The electron may be self-trapped in slab systems of GaN , AlN and alkali halides, if the slab systems are thinner than one over ten of the length unit ℏ/mc.

SURFACE POLARON SELF-ENERGY AND EFFECTIVE MASS IN A WURTZITE GaN NANOWIRE

2009 ◽  
Vol 23 (16) ◽  
pp. 3403-3416 ◽  
Author(s):  
LI ZHANG
Keyword(s):  
Effective Mass ◽  
Ground State ◽  
Bulk Material ◽  
Coupling Constants ◽  
Perturbation Approach ◽  
Polar Optical Phonon ◽  
Phonon Coupling ◽  
Phonon Modes ◽  
Self Trapping ◽  
Gan Nanowire

The ground-state self-trapping energy and effective mass of surface polarons in a freestanding wurtzite GaN nanowire (NW) are studied using the second-order perturbation approach. Based on the dielectric continuum and Loudon's uniaxial crystal models, the polar optical phonon modes in the one-dimensional (1D) systems are analyzed, and the vibrating spectra of surface optical (SO) modes and electron–SO phonon coupling functions are discussed and analyzed. The calculations of the ground-state polaron self-trapping energy and the correction of effective mass due to the SO phonon modes in the 1D GaN NWs reveal that the polaron self-trapping energy and the correction of effective mass is far larger than those in 1D GaAs NW systems. The reasons for this obvious difference in the two 1D structures can be attributed to the different electron–phonon coupling constants and electron effective masses of bulk material constituting the two types of 1D confined systems. Finally, the polaronic properties of the wurtzite 1D GaN NWs are compared with those of wurtzite GaN -based two-dimensional quantum wells. The physical origins leading to these characteristics and their distinction in the different-dimensionality systems is carefully analyzed.

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