Magneto-reflection spectroscopy of monolayer transition-metal dichalcogenide semiconductors in pulsed magnetic fields

TL;DR

This paper reports on polarization-resolved magneto-reflection spectroscopy of monolayer transition-metal dichalcogenides in pulsed magnetic fields up to 65 Tesla, revealing valley Zeeman effects and exciton properties.

Contribution

It introduces experimental techniques for high-field optical spectroscopy of monolayer TMDs and demonstrates how diamagnetic shifts inform exciton binding energy estimates.

Findings

Observation of valley Zeeman effect in WS₂ monolayers

Measurement of small exciton diamagnetic shifts

Model calculations linking shifts to exciton binding energy

Abstract

We describe recent experimental efforts to perform polarization-resolved optical spectroscopy of monolayer transition-metal dichalcogenide semiconductors in very large pulsed magnetic fields to 65 tesla. The experimental setup and technical challenges are discussed in detail, and temperature-dependent magneto-reflection spectra from atomically thin tungsten disulphide (WS$_2$) are presented. The data clearly reveal not only the valley Zeeman effect in these 2D semiconductors, but also the small quadratic exciton diamagnetic shift from which the very small exciton size can be directly inferred. Finally, we present model calculations that demonstrate how the measured diamagnetic shifts can be used to constrain estimates of the exciton binding energy in this new family of monolayer semiconductors.