Remote electron-phonon interactions and screening in Van der Waals heterostructures (T. Sohier)

This video is part of the ETSF Webinars series. It is given by Thibault Sohier, from Liege University (Belgium).
Stacking up 2D materials has proven to be a promising strategy to enhance or engineer the properties of materials for (opto)electronic applications. In order to select the right layer combinations and design optimal heterostructures, one first needs to understand the fundamental interactions between electrons and phonons in those systems. Beyond what happens within the individual layers, it is especially important to model and simulate the remote, interlayer aspects of electron-phonon physics. I will present a semi-analytical model of the electrostatics of Van der Waals heterostructures and how it can be used to simulate remote electron-phonon interactions and their screening [1]. The response of each layer is computed within density-functional perturbation theory, then combined semi-analytically to compute the response of an arbitrary stack of 2D layers. The system is perturbed with the electric fields generated by the polar-optical phonons of a given layer to simulate the remote and screened Fröhlich electron-phonon coupling. I will demonstrate the method's usefulness for material design with a GaSe/BN/graphene heterostructure in which free-carriers in graphene remotely screen the Frohlich electron-phonon coupling in GaSe, thus enhancing the mobility of this semiconductor at low doping [1].

[1] T. Sohier, M. Gibertini, M. Verstraete, "Remote free-carrier screening to boost the mobility of Fröhlich-limited 2D semiconductors", Physical Review Materials 5, 024004 (2021)