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DS: Fachverband Dünne Schichten
DS 3: Layer Properties
DS 3.4: Vortrag
Montag, 18. März 2024, 16:15–16:30, A 053
Are Xenes excitonic insulators? — •Olivia Pulci1, Paola Gori2, Davide Grassano3, Marco D’Alessandro4, and Friedhelm Bechstedt5 — 1Department of Physics, and INFN, University of Rome Tor Vergata, Italy — 2Department of Industrial, Electronic and Mechanical Engineering, Roma Tre University, Italy — 3Theory and Simulation of Materials (THEOS), Ecole Polytechnique Federale de Lausanne, Switzerland — 4Istituto di Struttura della Materia-CNR (ISM-CNR), Rome, Italy — 5Institut für Festkörpertheorie und -optik, Friedrich-Schiller-Universität Jena, Germany
Using a variational approach, the binding energies Eb of the lowest bound excitons in Xenes under varying electric field are investigated. The internal exciton motion is described both by Dirac electron dispersion and in effective-mass approximation, while the screened electron-hole attraction is modeled by a Rytova-Keldysh potential with a 2D electronic polarizability α2D. The relation between Eb and the spin-orbit gap Eg is ruled by the screening. The values of Eg and α2D are strongly modified by a vertical external electric bias U, which defines a transition from the topological into a trivial insulator at U = Eg /2, with the exception of plumbene. The existence of an excitonic insulator phase with Eb>Eg sensitively depends on the chosen α2D. Many-Body perturbation theory, applied to stanene, confirm the absence of an excitonic insulator phase, thus validating our results obtained by ab initio modeling of α2D.