# Large g factor in bilayer WS$_2$ flakes

## TL;DR

This paper reports a large valley Zeeman effect in bilayer WS$_2$, with an unusually high g factor of -16.5, due to interlayer recombination enabled by defect-induced symmetry breaking, opening new avenues for optical spin control.

## Contribution

It reveals a significantly enhanced g factor in bilayer WS$_2$ caused by interlayer recombination, a phenomenon enabled by defect-induced inversion symmetry breaking.

## Key findings

- Observed g factor as large as -16.5 in bilayer WS$_2$
- Interlayer recombination causes the large g factor
- Defect-induced symmetry breaking enables this effect

## Abstract

The valley of transition metal dichalcogenides provides an additional platform to manipulate spin due to its unique selection rule. Normally, intralayer optical transitions in magnetic field show a Zeeman splitting with g factor of about $-4$. Here we report remarkable valley Zeeman effect exhibited by splitting of excitonic emission in a bilayer WS$_{2}$, with a value of g factor as large as $-16.5$. The observed large g factor results from the interlayer recombination, as the conduction band and valence band are modified in opposite directions by magnetic field in different layers. The interlayer recombination is due to the defect induced inversion symmetry breaking, which is theoretically not accessible in ideal bilayer WS$_{2}$ with inversion symmetry. Large g factor of interlayer emission offers potential benefits for future optical spin control and detection.