Magneto photoluminescence measurements of tungsten disulphide monolayers

TL;DR

This study investigates the magnetic field effects on photoluminescence in monolayer tungsten disulphide, revealing valley splitting and determining g-factors for excitonic states at low temperatures.

Contribution

It provides experimental measurements of magnetic field-induced valley splitting and g-factors in CVD-grown WS2 monolayers, advancing understanding of their spin-valley coupling.

Findings

Magnetic field causes splitting of PL peaks in WS2 monolayers.

G-factors for exciton, trion, and bound excitons are quantified.

Valley degeneracy is lifted by magnetic fields up to 7 T.

Abstract

Layered transition-metal dichalcogenides have attracted great interest in the last few years. Thinned down to the monolayer limit they change from an indirect band structure to a direct band gap in the visible region. Due to the monolayer thickness the inversion symmetry of the crystal is broken and spin and valley are coupled to each other. The degeneracy between the two equivalent valleys, K and K', respectively, can be lifted by applying an external magnetic field. Here, we present photoluminescence measurements of CVD-grown tungsten disulphide (WS${_2}$) monolayers at temperatures of 2 K. By applying magnetic fields up to 7 T in Faraday geometry, a splitting of the photoluminescence peaks can be observed. The magnetic field dependence of the A-exciton, the trion and three bound exciton states is discussed and the corresponding g-factors are determined.