Pressure dependence of direct optical transitions in ReS2 and ReSe2

TL;DR

This study investigates how high hydrostatic pressure affects the electronic band structure and optical properties of ReS2 and ReSe2 using experimental photoreflectance spectroscopy and ab initio calculations, revealing pressure-dependent shifts in excitonic transitions.

Contribution

It provides the first combined experimental and theoretical analysis of pressure effects on the electronic structure of ReS2 and ReSe2, including detailed orbital and interlayer interaction insights.

Findings

Pressure coefficients for excitonic transitions are experimentally determined.

Transitions are assigned to the Z k-point and other off-high-symmetry points.

Anisotropic optical properties under pressure are characterized.

Abstract

We present an experimental and theoretical study of the electronic band structure of ReS2 and ReSe2 at high hydrostatic pressures. The experiments are performed by photoreflectance spectroscopy and are analyzed in terms of ab initio calculations within the density functional theory. Experimental pressure coefficients for the two most dominant excitonic transitions are obtained and compared with those predicted by the calculations. We assign the transitions to the Z k-point of the Brillouin zone and other k-points located away from highsymmetry points. The origin of the pressure coefficients of the measured direct transitions is discussed in terms of orbital analysis of the electronic structure and van der Waals interlayer interaction. The anisotropic optical properties are studied at high pressure by means of polarization-resolved photoreflectance measurements.