Carrier Mobility of Strongly Anharmonic Materials from First Principles

TL;DR

This paper introduces a non-perturbative, stochastic method combining ab initio molecular dynamics and the Kubo-Greenwood formalism to accurately calculate carrier mobilities in strongly anharmonic materials, surpassing traditional quasi-particle approaches.

Contribution

It develops a novel, non-perturbative approach for computing carrier mobilities that accounts for all orders of anharmonic and electron-vibrational couplings in strongly anharmonic materials.

Findings

Demonstrated the method on SrTiO3 and BaTiO3 across various temperatures.

Showed mobility trends are driven by anharmonic, higher-order couplings.

Rationalized temperature-dependent mobility using non-perturbative spectral functions.

Abstract

First-principle approaches for phonon-limited electronic transport are typically based on many-body perturbation theory and transport equations. With that, they rely on the validity of the quasi-particle picture for electrons and phonons, which is known to fail in strongly anharmonic systems. In this work, we demonstrated the relevance of effects beyond the quasi-particle picture by combining ab initio molecular dynamics and the Kubo-Greenwood (KG) formalism to establish a non-perturbative, stochastic method to calculate carrier mobilities while accounting for all orders of anharmonic and electron-vibrational couplings. In particular, we propose and exploit several numerical strategies that overcome the notoriously slow convergence of the KG formalism for both electronic and nuclear degree of freedom in crystalline solids. The capability of this method is demonstrated by calculating the temperature-dependent electron mobility of the strongly anharmonic oxide perovskites SrTiO3 and BaTiO3 across a wide range of temperatures. We show that the temperature-dependence of the mobility is largely driven by anharmonic, higher-order coupling effects and rationalize these trends in terms of the non-perturbative electronic spectral functions.