Volume 42, Number 5, June 1998
|Page(s)||523 - 528|
|Section||Condensed matter: electronic structure, electrical, magnetic and optical properties|
|Published online||01 September 2002|
The small-polaron crossover: Comparison between exact results and vertex correction approximation
Dipartimento di Fisica, Università di Roma
“La Sapienza” P.le A. Moro 2, 00185 Roma, Italy
2 Dipartimento di Fisica, Università di L'Aquila via Vetoio, 67100 Coppito-L'Aquila, Italy and INFM, Unità di L'Aquila
3 INFM, Unità di Roma 1, Dipartimento di Fisica, Università di Roma I “La Sapienza” P.le A. Moro 2, 00185 Roma, Italy
Accepted: 8 April 1998
We study the crossover from quasi-free electron to small polaron in the Holstein model for a single electron by means of both exact and self-consistent calculations in one dimension and on an infinite coordination lattice. We show that the crossover occurs when both strong coupling () and multiphonon () conditions are fulfilled leading to different relevant coupling constants (λ) in the adiabatic and () antiadiabatic region of the parameters space. We also show that the self-consistent calculations obtained by including the first electron-phonon vertex correction give accurate results in a sizeable region of the phase diagram well separated from the polaronic crossover.
PACS: 71.38.+i – Polarons and electron-phonon interactions / 63.20.Kr – Phonon-electron and phonon-phonon interactions
© EDP Sciences, 1998
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