Berlin 2018 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 2: 2D Materials: Session I (joint session DS/CPP/HL)
DS 2.7: Vortrag
Montag, 12. März 2018, 11:00–11:15, H 2032
Density-functional perturbation theory for gated 2D heterostructures — •Thibault Sohier1, Marco Gibertini1, Nicola Marzari1, Matteo Calandra2, and Francesco Mauri3 — 1THEOS and MARVEL, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland — 2IMPMC, CNRS, Université Pierre et Marie Curie, Paris, France — 3Departimento di Fisica, Università di Roma La Sapienza, Roma, Italy
The ability to perform first-principles calculations of phonons and electron-phonon interactions in gated 2D heterostructures is crucial to the understanding and design of next-generation devices. Yet, standard methods relying on 3D periodic-boundary conditions fail to properly account for the consequences of dimensionality and the field-effect on electron-phonon physics. Here we present an implementation of density-functional perturbation theory using open boundary conditions adequate to the simulation of 2D systems, and with the possibility to add charged planes to emulate the doping of the slab via field-effect. We first illustrate the importance of working in the correct 2D framework with the study of long-wavelength phonons in polar materials, focusing on two mechanisms relevant for the performances of electronic devices: the Fröhlich interaction and the LO-TO splitting. Second, we address the consequences of the field-effect setup by looking at flexural phonons and their coupling to electrons in gated graphene. We observe that unlike isolated graphene, the coupling with flexural phonons in gated graphene is not forbidden by symmetry, but it is strongly suppressed by electronic screening.