Anharmonic Lattice Dynamics and Electron-Phonon Coupling Calculations Made Simple (M. Zacharias)

Anharmonicity and electron-phonon coupling have been central for decades in condensed matter research. As we progress in developing robust computational methods to address anharmonicity and electron-phonon coupling individually, there is an increasing need to seamlessly integrate both on a unified platform. In this talk, I will discuss how the anharmonic special displacement method (A-SDM) [1,2] can serve as a simple and efficient tool towards ab-initio anharmonic electron-phonon coupling calculations. In particular, I will show that the A-SDM removes the need for extensive sampling of the nuclear configuration space performed in stochastic or molecular dynamics simulations. In the A-SDM, only a handful of configurations suffice to capture both the effective temperature-dependent potential energy surface and its interplay with the electronic structure, streamlining the process with efficiency. I will demonstrate the capabilities of the method in the challenging regime of locally disordered and strongly anharmonic materials, like metal halide perovskites [3]. I will also elucidate the underlying physical concepts within the A-SDM and provide an overview of its advantages and limitations. Finally, I will indicate avenues for future work in ab-initio calculations at finite temperatures, including examples of temperature-dependent anharmonic phonons, band structures, absorption and transport coefficients, as well as exploring exciton-phonon and ultrafast phenomena [4].

References: [1] M. Zacharias, G. Volonakis, F. Giustino, J. Even Phys. Rev. B 108, 035155 (2023) [2] M. Zacharias, F. Giustino, Phys. Rev. Research 2, 013357 (2020) [3] M. Zacharias, G. Volonakis, F. Giustino, J. Even npj Comput. Mater. 9, 153 (2023) [4] L. Hyungjun, et al., EPW code, npj Comput Mater 9, 156 (2023)

Acknowledgments: I acknowledge funding from the European Union (project ULTRA-2DPK / HORIZON-MSCA-2022-PF-01 / Grant Agreement No. 101106654). Views and opinions expressed are however those of the authors only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the granting authority can be held responsible for them.