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Title: Polarons and bipolarons in strongly interacting electron-phonon systems

Abstract

The Holstein Hubbard and Holstein {ital t}-{ital J} models are studied for a wide range of phonon frequencies, electron-electron, and electron-phonon interaction strengths on finite lattices with up to ten sites by means of direct Lanczos diagonalization. Previously the necessary truncation of the phononic Hilbert space caused serious limitations to either very small systems (four or even two sites) or to weak electron-phonon coupling, in particular in the adiabatic regime. Using parallel computers we were able to investigate the transition from {open_quote}{open_quote}large{close_quote}{close_quote} to {open_quote}{open_quote}small{close_quote}{close_quote} polarons in detail. By resolving the low-lying eigenstates of the Hamiltonian and by calculating the spectral function, we can identify a polaron band in the strong-coupling case, whose dispersion deviates from the free-particle dispersion at low and intermediate phonon frequencies. For two electrons (holes) we establish the existence of bipolaronic states and discuss the formation of a bipolaron band. For the two-dimensional Holstein {ital t}-{ital J} model, we demonstrate that the formation of hole polarons is favored by strong Coulomb correlations. Analyzing hole-hole correlation functions, we find that hole binding is enhanced as a dynamical effect of the electron-phonon interaction. {copyright} {ital 1996 The American Physical Society.}

Authors:
; ;  [1]
  1. Physikalisches Institut, Universitaet Bayreuth, D-95440 Bayreuth (Germany)
Publication Date:
OSTI Identifier:
280227
Resource Type:
Journal Article
Journal Name:
Physical Review, B: Condensed Matter
Additional Journal Information:
Journal Volume: 53; Journal Issue: 15; Other Information: PBD: Apr 1996
Country of Publication:
United States
Language:
English
Subject:
66 PHYSICS; MATHEMATICAL MODELS; ELECTRON-PHONON COUPLING; SUPERCONDUCTIVITY; ELECTRON CORRELATION; POLARONS; HIGH-TC SUPERCONDUCTORS; DISPERSION RELATIONS; CUPRATES; NICKEL OXIDES; ELECTRON PAIRS; CHARGE TRANSPORT

Citation Formats

Wellein, G, Roeder, H, and Fehske, H. Polarons and bipolarons in strongly interacting electron-phonon systems. United States: N. p., 1996. Web. doi:10.1103/PhysRevB.53.9666.
Wellein, G, Roeder, H, & Fehske, H. Polarons and bipolarons in strongly interacting electron-phonon systems. United States. doi:10.1103/PhysRevB.53.9666.
Wellein, G, Roeder, H, and Fehske, H. Mon . "Polarons and bipolarons in strongly interacting electron-phonon systems". United States. doi:10.1103/PhysRevB.53.9666.
@article{osti_280227,
title = {Polarons and bipolarons in strongly interacting electron-phonon systems},
author = {Wellein, G and Roeder, H and Fehske, H},
abstractNote = {The Holstein Hubbard and Holstein {ital t}-{ital J} models are studied for a wide range of phonon frequencies, electron-electron, and electron-phonon interaction strengths on finite lattices with up to ten sites by means of direct Lanczos diagonalization. Previously the necessary truncation of the phononic Hilbert space caused serious limitations to either very small systems (four or even two sites) or to weak electron-phonon coupling, in particular in the adiabatic regime. Using parallel computers we were able to investigate the transition from {open_quote}{open_quote}large{close_quote}{close_quote} to {open_quote}{open_quote}small{close_quote}{close_quote} polarons in detail. By resolving the low-lying eigenstates of the Hamiltonian and by calculating the spectral function, we can identify a polaron band in the strong-coupling case, whose dispersion deviates from the free-particle dispersion at low and intermediate phonon frequencies. For two electrons (holes) we establish the existence of bipolaronic states and discuss the formation of a bipolaron band. For the two-dimensional Holstein {ital t}-{ital J} model, we demonstrate that the formation of hole polarons is favored by strong Coulomb correlations. Analyzing hole-hole correlation functions, we find that hole binding is enhanced as a dynamical effect of the electron-phonon interaction. {copyright} {ital 1996 The American Physical Society.}},
doi = {10.1103/PhysRevB.53.9666},
journal = {Physical Review, B: Condensed Matter},
number = 15,
volume = 53,
place = {United States},
year = {1996},
month = {4}
}