Electron-Phonon Coupling from First-Principles

TH Department Seminar
Date: Oct 12, 2023
Time: 02:00 PM (Local Time Germany)
Speaker: Prof. Samuel Poncé
Université catholique de Louvain, Institute of Condensed Matter and Nanosciences, Louvain-la-Neuve, Belgium
Location: https://zoom.us/j/92017039549?pwd=QkFtR0xLMWttZi9ackNiZFdoNnlpZz09
Room: Meeting ID: 920 1703 9549 | Passcode: 122127
Host: TH Department

For this talk, I will highlight the importance of electron-phonon interaction to describe many experimental phenomena including carrier mobility, phonon-assisted optical absorption, phonon-limited superconductivity, zero-point renormalization, temperature dependence of the bandgaps, electron mass enhancement and polaron liquids.I will show how to derive and efficiently compute electron-phonon interaction from first principles focusing on two manifestations of the electron-phonon coupling: carrier mobility and temperature dependence of the bandgap.

I will first present the Boltzmann transport equation within the general framework of the quantum theory of mobility. I will subsequently discuss the accuracy limit of ab initio electron-phonon calculations of carrier mobilities and show that predictive calculations of electron and hole mobilities require an extremely fine sampling of inelastic scattering processes in momentum space. Such fine sampling calculation is made possible at an affordable computational cost through the use of efficient Fourier-Wannier interpolation of the electron-phonon matrix elements. Using that interpolation technique, I will present recent findings on the intrinsic electron and hole mobility of silicon, wurtzite GaN, and halide perovskites.
In particular, the effect of magnetic field on the carrier transport properties will be discussed in the context of Hall mobility measurements.
In addition, recent advances have allowed for the extension of the theory to the realms of 2D materials and I will present results on monolayers such as MoS2, InSe or SnS2.

Finally, I will discuss the Allen-Heine-Cardona (AHC) theory for the renormalization of the electronic bandstructure with temperature. In particular, I will show that the adiabatic AHC theory allows for an easy computation of the effect of electron-phonon interactions but cannot be used in the case of infrared-active materials where a nonadiabatic version is required.