Coherent charge carrier dynamics in the presence of thermal lattice vibrations

TL;DR

This paper introduces a coherent state framework for lattice vibrations to analyze charge carrier dynamics, revealing phenomena like transient localization and band tail formation due to self-generated disorder, which traditional methods cannot explain.

Contribution

It develops a novel coherent state approach to lattice vibrations, bridging quantum optics and condensed matter physics, and uncovers new insights into charge carrier coherence and disorder effects.

Findings

Transient localization at high temperatures due to coherence.

Band tails in density of states from self-generated disorder.

Exact agreement with conventional perturbation theory.

Abstract

We develop the coherent state representation of lattice vibrations to describe their interactions with charge carriers. In direct analogy to quantum optics, the coherent state representation leads from quantized lattice vibrations (phonons) naturally to a quasiclassical field limit, i.e., the deformation potential. To an electron, the deformation field is a sea of hills and valleys, as ``real'' as any external field, morphing and propagating at the sound speed, and growing in magnitude with temperature. In this disordered potential landscape, the charge carrier dynamics is treated nonperturbatively, preserving their coherence beyond single collision events. We show the coherent state picture agrees exactly with the conventional Fock state picture in perturbation theory. Furthermore, it goes beyond by revealing aspects that the conventional theory could not explain: transient localization even at high temperatures by charge carrier coherence effects, and band tails in the density of states due to the self-generated disorder (deformation) potential in a pure crystal. The coherent state paradigm of lattice vibrations supplies tools for probing important questions in condensed matter physics as in quantum optics.