Semimetallicity and electron-hole liquid in two-dimensional C and BN based compounds

Alejandro Lopez-Bezanilla and Peter B. Littlewood

Phys. Rev. Materials 5, 014006 – Published 29 January 2021

Abstract

An insulating-metallic transition mediated by substitutional atoms is predicted in a series of two-dimensional carbon-based structures. Introducing Si atoms in selected sites of tetrahexcarbon [B. Ram and H. Mizuseki, Carbon 137, 266 (2018)] according to rational chemical rules, metallicity by trivial band inversion without a band gap opening is induced. Additional substitution of the remaining C atoms by BN dimers introduces no changes in the metallic properties. A series of isomorphous two-dimensional materials with isoelectronic structures derived by exchanging group IV elements exhibiting various band gaps is obtained. Dynamical stability is verified with a phonon analysis and beyond the harmonic approximation with molecular dynamics up to room temperature. The semimetallic compounds have well-nested pockets of carriers and are good candidates for the formation of an excitonic insulator.

Received 20 August 2020
Revised 17 October 2020
Accepted 14 January 2021

DOI:https://doi.org/10.1103/PhysRevMaterials.5.014006

Physics Subject Headings (PhySH)

Excitons

Two-dimensional electron system

Density functional calculations

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Alejandro Lopez-Bezanilla ¹ and Peter B. Littlewood ^2,3,*

¹Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
²Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois, 60439, USA
³James Franck Institute, University of Chicago, Chicago, Illinois 60637, USA