Polarons

Edwards, James Lloyd

An effective interaction potential for a pair of polarons is derived in a Landau-Pekar adiabatic approximation.The possibility of formation of bound states of two polarons is discussed.The lowlying energy states of a system of Landau-Pekar polarons interacting with the derived effective potential are investigated by employing approximation models including a body-centered cubic lattice of polarons, a Hartree-Fock gas of polarons, and a Hartree-Fock gas of polarons weakly coupled to a polaron plasma.The low-lying energy states based on these models are examined numerically for a specific test case intended to describe polarons in an ionic crystal with a polaron coupling constant large enough that the Landau-Pekar approximation may be expected to be appropriate.It is found that, for a wide range of polaron densities, the plasma-coupled gas model yields the best results among the models treated.

G. Höhler

E. A. Kochetov, S.P. Kuleshov, Smondyrev

A general approach to the investigation of polaron systems using path integrals is presented. The basis of the approach is a functional variational method which generalizes Feynman's to the case of a nonvanishing momentum of the system. The characteristics of a free polaron and the behavior of a polaron system in the presence of weak external perturbations are investigated. Questions associated with polaron thermodynamics are considered. The high-temperature behavior of the mean energy and the polaron mass are studied, as is the reaction of a polaron system at finite temperatures to an external perturbation.

Maoxin Liu, Zu‐Jian Ying, Jun‐Hong An +2 more

Abstract The concept of the polaron in condensed matter physics has been extended to the Rabi model, where polarons resulting from the coupling between a two-level system and single-mode photons represent two oppositely displaced oscillators. Interestingly, tunneling between these two displaced oscillators can induce an anti-polaron, which has not been systematically explored in the literature, especially in the presence of an asymmetric term. In this paper, we present a systematic analysis of the competition between the polaron and anti-polaron under the interplay of the coupling strength and the asymmetric term. While intuitively the anti-polaron should be secondary owing to its higher potential energy, we find that, under certain conditions, the minor anti-polaron may gain a reversal in the weight over the major polaron. If the asymmetric amplitude ϵ is smaller than the harmonic frequency ω , such an overweighted anti-polaron can occur beyond a critical value of the coupling strength g ; if ϵ is larger, the anti-polaron can even be always overweighted at any g . We propose that the explicit occurrence of the overweighted anti-polaron can be monitored by a displacement transition from negative to positive values. This displacement is an experimentally accessible observable, which can be measured by quantum optical methods, such as balanced Homodyne detection.

Toshio Yokota