First-principles method for electron-phonon coupling and electron mobility: Applications to 2D materials

TL;DR

This paper develops a first-principles computational method to accurately calculate electron-phonon interactions and electron mobility in 2D materials like graphene, silicene, and MoS2, providing insights into their transport properties.

Contribution

It introduces a fully numerical first-principles approach to evaluate electron-phonon coupling and mobility, capturing anisotropy and inelastic scattering without semi-analytic approximations.

Findings

Graphene exhibits over an order of magnitude higher mobility than silicene.

Silicene shows strong interaction with out-of-plane phonon modes.

Calculated mobilities for MoS2 align with recent theoretical results.

Abstract

We present density functional theory calculations of the phonon-limited mobility in n-type monolayer graphene, silicene and MoS$_2$. The material properties, including the electron-phonon interaction, are calculated from first-principles. We provide a detailed description of the normalized full-band relaxation time approximation for the linearized Boltzmann transport equation (BTE) that includes inelastic scattering processes. The bulk electron-phonon coupling is evaluated by a supercell method. The method employed is fully numerical and does therefore not require a semi-analytic treatment of part of the problem and, importantly, it keeps the anisotropy information stored in the coupling as well as the band structure. In addition, we perform calculations of the low-field mobility and its dependence on carrier density and temperature to obtain a better understanding of transport in graphene, silicene and monolayer MoS$_2$. Unlike graphene, the carriers in silicene show strong interaction with the out-of-plane modes. We find that graphene has more than an order of magnitude higher mobility compared to silicene. For MoS$_2$, we obtain several orders of magnitude lower mobilities in agreement with other recent theoretical results. The simulations illustrate the predictive capabilities of the newly implemented BTE solver applied in simulation tools based on first-principles and localized basis sets.