Spectral Properties of Holstein and Breathing Polarons
- University of Cincinnati
- University of British Columbia, Vancouver
- ORNL
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, iii) in the Holstein model the quasiparticle dispersion displays a kink and a small gap at an excitation energy equal to the phonon frequency $$\omega_0$$ while in the breathing model it displays two gaps, one at excitation energy $$\omega_0$$ and another one at $$2\omega_0$$. 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 which situation the difference between the two models becomes less significant.
- Research Organization:
- Oak Ridge National Laboratory (ORNL); Center for Nanophase Materials Sciences; Center for Computational Sciences
- Sponsoring Organization:
- SC USDOE - Office of Science (SC)
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 1003486
- Journal Information:
- Physical Review B, Journal Name: Physical Review B Journal Issue: 20 Vol. 73; ISSN 1098-0121; ISSN 1550-235X
- Country of Publication:
- United States
- Language:
- English
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