Electrons and phonons in single layers of hexagonal indium chalcogenides from ab initio calculations

Zolyomi, V. and Drummond, N. D. and Falko, Vladimir (2014) Electrons and phonons in single layers of hexagonal indium chalcogenides from ab initio calculations. Physical review B, 89 (20). ISSN 1098-0121

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Abstract

We use density functional theory to calculate the electronic band structures, cohesive energies, phonon dispersions, and optical absorption spectra of two-dimensional In2X2 crystals, where X is S, Se, or Te. We identify two crystalline phases (alpha and beta) of monolayers of hexagonal In2X2, 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 In2X2) at hole concentrations n(S) = 6.86 x 10(13) cm(-2), n(Se) = 6.20 x 10(13) cm(-2), and n(Te) = 2.86 x 10(13) cm(-2) for X= S, Se, and Te, respectively, for alpha-In2X2 and n(S) = 8.32 x 10(13) cm(-2), n(Se) = 6.00 x 10(13) cm(-2), and n(Te) = 8.14 x 10(13) cm(-2) for beta-In2X2.

Item Type:
Journal Article
Journal or Publication Title:
Physical review B
Additional Information:
©2014 American Physical Society
Subjects:
ID Code:
70130
Deposited By:
Deposited On:
29 Jul 2014 09:53
Refereed?:
Yes
Published?:
Published
Last Modified:
12 Jul 2020 04:45