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

V. Zolyomi; N. D. Drummond; V. I. Fal'ko

doi:10.1103/PhysRevB.89.205416

paper

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

arXiv:1403.4389 · doi:10.1103/PhysRevB.89.205416

Abstract

We use density functional theory to calculate the electronic band structures, cohesive energies, phonon dispersions, and optical absorption spectra of two-dimensional In $_{2}$ X $_{2}$ crystals, where X is S, Se, or Te. We identify two crystalline phases (alpha and beta) of monolayers of hexagonal In $_{2}$ X $_{2}$ , 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 $_{2}$ X $_{2}$ ) at hole concentrations $n_{S} = 6.86 \times 1 0^{13}$ cm $^{- 2}$ , $n_{Se} = 6.20 \times 1 0^{13}$ cm $^{- 2}$ , and $n_{Te} = 2.86 \times 1 0^{13}$ cm $^{- 2}$ for X=S, Se, and Te, respectively, for alpha-In $_{2}$ X $_{2}$ and $n_{S} = 8.32 \times 1 0^{13}$ cm $^{- 2}$ , $n_{Se} = 6.00 \times 1 0^{13}$ cm $^{- 2}$ , and $n_{Te} = 8.14 \times 1 0^{13}$ cm $^{- 2}$ for beta-In $_{2}$ X $_{2}$ .

9 pages. arXiv admin note: text overlap with arXiv:1302.6067

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

Abstract

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