Trapping of lattice polarons by impurities

TL;DR

This paper investigates how single impurities affect polaron behavior in three dimensions, revealing that even small impurities can trap polarons, especially under certain coupling and phonon frequency conditions.

Contribution

It introduces an efficient continuous time quantum Monte-Carlo method for exact treatment of phonons and computes the polaron trapping diagram in 3D with impurities.

Findings

Small impurities can trap polarons at intermediate coupling and low phonon frequency.

Polaron trapping requires relatively small impurity potentials.

Number of phonons increases significantly upon trapping.

Abstract

We consider the effects of single impurities on polarons in three-dimensions (3D) using a continuous time quantum Monte-Carlo algorithm. An exact treatment of the phonon degrees of freedom leads to a very efficient algorithm and we are able to compute the polaron dynamics on an infinite lattice using an auxiliary weighting scheme. The magnitude of the impurity potential, the electron-phonon coupling and the phonon frequency are varied. We determine the magnitude of the impurity potential required for polaron trapping. For small electron-phonon coupling the number of phonons increases dramatically on trapping. The polaron binding diagram is computed, showing that intermediate-coupling low-phonon-frequency polarons are localized by exceptionally small impurities.