Title: Valence band inversion and spin-orbit effects in the electronic structure of monolayer GaSe

Abstract

Two-dimensional monochalcogenides (MX) have been identified as a unique and promising class of layered materials in recent years. The valence band of single-layer MX, as predicted by theory, is inverted into a bow-shaped (often referred to as an inverted sombrero) and relatively flat dispersion, which is expected to give rise to strongly correlated effects. The inversion leads to an indirect band gap, which is consistent with photoluminescence (PL) experiments, but PL provides no direct evidence of the band inversion in the valence band. Here we demonstrate for a hexagonal MX crystal, gallium selenide (GaSe), using a combination of angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT), that the valence band of monolayer (ML) GaSe exhibits a robust inversion of the valence dispersion at the Γ point forming a bow-shaped dispersion with a depth of 120 ± 10 meV between the double valence band maximum along the ΓK direction. We also demonstrate that the deeper-lying bands detected in the ARPES spectrum are consistent with DFT calculations only if spin-orbit coupling is considered. The presented ARPES evidence that spin-orbit coupling leads to the splitting of two fourfold-degenerate states into four Kramers doublets is of significance for PL measurements, as the changemore » in energy of the second highest valence state at the Γ point has a measurable effect on the PL energies in high-energy luminescence. Here, e predict the optical absorption coefficients for the principal transitions in ML GaSe using a four-band k∙p model parametrized from first-principles theory with spin-orbit effects considered.« less

Authors:

Ben Aziza, Zeineb ^[1]; Zólyomi, Viktor ^[2]; Henck, Hugo ^[1]; Pierucci, Debora ^[3]; Silly, Mathieu G. ^[4]; Avila, José ^[4]; Magorrian, Samuel J. ^[2]; Chaste, Julien ^[1]; Chen, Chaoyu ^[4]; Yoon, Mina  ^[5];

• Search DOE PAGES for author "Yoon, Mina"
• Search DOE PAGES for ORCID "0000-0002-1317-3301"

Xiao, Kai  ^[6];

• Search DOE PAGES for author "Xiao, Kai"
• Search DOE PAGES for ORCID "0000-0002-0402-8276"

Sirotti, Fausto ^[4]; Asensio, Maria C. ^[4]; Lhuillier, Emmanuel ^[7]; Eddrief, Mahmoud ^[7]; Fal'ko, Vladimir I. ^[2]; Ouerghi, Abdelkarim ^[1]

---

+ Show Author Affiliations

1. Centre de Nanosciences et de Nanotechnologies, Marcoussis, (France); Centre National de la Recherche Scientifique (CNRS), Paris (France); Univ. Paris-Saclay, Gif-sur-Yvette (France); Univ. Paris-Sud, Orsay (France)
2. Univ. of Manchester (United Kingdom). National Graphene Inst.
3. CELLS-ALBA Synchrotron Radiation Facility, Barcelona (Spain)
4. Synchrotron SOLEIL, Saint-Aubin (France); Univ. Paris-Saclay, Gif-sur-Yvette (France)
5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS); Univ. of Tennessee, Knoxville, TN (United States)
6. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS)
7. Sorbonne Universités, Paris (France). Inst. des NanoSciences de Paris (INSP)

Publication Date:

Tue Sep 04 00:00:00 EDT 2018

Research Org.:

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1494886

Alternate Identifier(s):

OSTI ID: 1468859

Grant/Contract Number:  

AC05-00OR22725

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review B

Additional Journal Information:

Journal Volume: 98; Journal Issue: 11; Journal ID: ISSN 2469-9950

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY