TY - JOUR

T1 - Spectral properties of Holstein and breathing polarons

AU - Slezak, C.

AU - Macridin, A.

AU - Sawatzky, G. A.

AU - Jarrell, M.

AU - Maier, T. A.

PY - 2006

Y1 - 2006

N2 - We calculate the spectral properties of the one-dimensional Holstein and breathing polarons using the self-consistent Born approximation. The Holstein model electron-phonon coupling is momentum independent while the breathing coupling increases monotonically with the phonon momentum. We find that for a linear or tight binding electron dispersion: (i) for the same value of the dimensionless coupling the quasiparticle renormalization at small momentum in the breathing polaron is much smaller, (ii) the quasiparticle renormalization at small momentum in the breathing polaron increases with phonon frequency unlike in the Holstein model where it decreases, and (iii) in the Holstein model the quasiparticle dispersion displays a kink and a small gap at an excitation energy equal to the phonon frequency ω0 while in the breathing model it displays two gaps, one at excitation energy ω0 and another one at 2 ω0. These differences have two reasons: first, the momentum of the relevant scattered phonons increases with increasing polaron momentum and second, the breathing bare coupling is an increasing function of the phonon momentum. These result in an effective electron-phonon coupling for the breathing model which is an increasing function of the total polaron momentum, such that the small momentum polaron is in the weak coupling regime while the large momentum one is in the strong coupling regime. However, the first reason does not hold if the free electron dispersion has low energy states separated by large momentum, as in a higher dimensional system, for example, in this situation the difference between the two models becomes less significant.

AB - We calculate the spectral properties of the one-dimensional Holstein and breathing polarons using the self-consistent Born approximation. The Holstein model electron-phonon coupling is momentum independent while the breathing coupling increases monotonically with the phonon momentum. We find that for a linear or tight binding electron dispersion: (i) for the same value of the dimensionless coupling the quasiparticle renormalization at small momentum in the breathing polaron is much smaller, (ii) the quasiparticle renormalization at small momentum in the breathing polaron increases with phonon frequency unlike in the Holstein model where it decreases, and (iii) in the Holstein model the quasiparticle dispersion displays a kink and a small gap at an excitation energy equal to the phonon frequency ω0 while in the breathing model it displays two gaps, one at excitation energy ω0 and another one at 2 ω0. These differences have two reasons: first, the momentum of the relevant scattered phonons increases with increasing polaron momentum and second, the breathing bare coupling is an increasing function of the phonon momentum. These result in an effective electron-phonon coupling for the breathing model which is an increasing function of the total polaron momentum, such that the small momentum polaron is in the weak coupling regime while the large momentum one is in the strong coupling regime. However, the first reason does not hold if the free electron dispersion has low energy states separated by large momentum, as in a higher dimensional system, for example, in this situation the difference between the two models becomes less significant.

UR - http://www.scopus.com/inward/record.url?scp=33744775722&partnerID=8YFLogxK

U2 - 10.1103/PhysRevB.73.205122

DO - 10.1103/PhysRevB.73.205122

M3 - Article

AN - SCOPUS:33744775722

SN - 1098-0121

VL - 73

JO - Physical Review B - Condensed Matter and Materials Physics

JF - Physical Review B - Condensed Matter and Materials Physics

IS - 20

M1 - 205122

ER -