Electron-Phonon Scattering in the Presence of Soft Modes and Electron Mobility in SrTiO$_{3}$ Perovskite from First Principles

TL;DR

This paper introduces a first-principles method to calculate electron-phonon interactions and charge transport in anharmonic crystals with soft modes, accurately predicting electron mobility in SrTiO$_{3}$ across a range of temperatures.

Contribution

The authors develop a novel approach using renormalized phonons to account for anharmonic effects in electron-phonon coupling calculations, applicable to materials with phase transitions.

Findings

Electron mobility in SrTiO$_{3}$ is mainly limited by optical phonons at room temperature.

Soft ferroelectric phonons dominate scattering below 200 K.

The method accurately reproduces the temperature dependence of mobility between 150-300 K.

Abstract

Structural phase transitions and soft phonon modes pose a longstanding challenge to computing electron-phonon (e-ph) interactions in strongly anharmonic crystals. Here we develop a first-principles approach to compute e-ph scattering and charge transport in materials with anharmonic lattice dynamics. Our approach employs renormalized phonons to compute the temperature-dependent e-ph coupling for all phonon modes, including the soft modes associated with ferroelectricity and phase transitions. We show that the electron mobility in cubic SrTiO$_{3}$ is controlled by scattering with longitudinal optical phonons at room temperature and with ferroelectric soft phonons below 200~K. Our calculations can accurately predict the temperature dependence of the electron mobility in SrTiO$_{3}$ between 150$-$300~K, and reveal the microscopic origin of its roughly $T^{-3}$ trend. Our approach enables first-principles calculations of e-ph interactions and charge transport in broad classes of crystals with phase transitions and strongly anharmonic phonons.