Electronic bandstructure and van der Waals coupling of ReSe2 revealed by high-resolution angle-resolved photoemission spectroscopy

TL;DR

This study uses high-resolution angle-resolved photoemission spectroscopy to reveal the highly anisotropic electronic band structure and significant interlayer van der Waals coupling in bulk ReSe2, a layered transition metal dichalcogenide.

Contribution

First direct nanoscale ARPES measurement of ReSe2's electronic structure, demonstrating anisotropy and interlayer coupling consistent with DFT calculations.

Findings

Valence band maxima are away from high-symmetry points.

Effective mass doubles perpendicular to Re chains.

Interlayer van der Waals coupling causes notable electronic dispersion.

Abstract

ReSe2 and ReS2 are unusual compounds amongst the layered transition metal dichalcogenides as a result of their low symmetry, with a characteristic in-plane anisotropy due to in-plane rhenium chains. They preserve inversion symmetry independent of the number of layers and, in contrast to more well-known transition metal dichalcogenides, bulk and few-monolayer Re-TMD compounds have been proposed to behave as electronically and vibrational decoupled layers. Here, we probe for the first time the electronic band structure of bulk ReSe2 by direct nanoscale angle-resolved photoemission spectroscopy. We find a highly anisotropic in- and out-of-plane electronic structure, with the valence band maxima located away from any particular high-symmetry direction. The effective mass doubles its value perpendicular to the Re chains and the interlayer van der Waals coupling generates significant electronic dispersion normal to the layers. Our density functional theory calculations, including spin-orbit effects, are in excellent agreement with these experimental findings.