Abstract
We use density functional theory to calculate the electronic band structures, cohesive energies, phonon dispersions, and optical absorption spectra of two-dimensional In crystals, where X is S, Se, or Te. We identify two crystalline phases ( and ) of monolayers of hexagonal In, and show that they are characterized by different sets of Raman-active phonon modes. We find that these materials are indirect-band-gap semiconductors with a sombrero-shaped dispersion of holes near the valence-band edge. The latter feature results in a Lifshitz transition (a change in the Fermi-surface topology of hole-doped In) at hole concentrations cm, cm, and cm for X=S, Se, and Te, respectively, for -In and cm, cm, and cm for -In.
- Received 16 March 2014
DOI:https://doi.org/10.1103/PhysRevB.89.205416
©2014 American Physical Society