Electron-phonon coupling from first-principles

日時　2022年11月24日　（木）　17：00～18：00
場所　オンライン(Zoom形式)
講師　Samuel Poncé
(Université catholique de Louvain)

For this seminar, 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: temperature dependence of the bandgap and carrier mobility.

The renormalization of electronic eigenenergies due to electron-phonon interactions (temperature dependence and zero-point motion effect) is important in many materials.
We study the Allen-Heine-Cardona (AHC) theory of the renormalization in a first-principle context. The AHC theory relies on the rigid-ion approximation, and naturally leads to a self-energy (Fan) contribution and a Debye-Waller contribution [1]. 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 [2,3].

Finally, I will present the Boltzmann transport equation within the general framework of the quantum theory of mobility [4]. 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 [5,6]. 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 [7].
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.

[1] S. Poncé et al., Phys. Rev. B 90, 214304 (2014)
[2] S. Poncé et al., J. Chem. Phys. 143, 102813 (2015)
[3] A. Miglio et al., npj Comput. Mater. 6, 167 (2020)
[4] S. Poncé et al., Rep. Prog. Phys. 83, 036501 (2020)
[5] F. Giustino et al., Phys. Rev. B 76, 165108 (2007)
[6] S. Poncé et al., Comput. Phys. Commun. 209, 116 (2016)
[7] S. Poncé et al., Phys. Rev. Research 3, 043022 (2021)

問合せ先　出田真一郎、島田賢也（放射光科学研究センター）