Valley Manipulation by Optically Tuning the Magnetic Proximity Effect in WSe$_2$/CrI$_3$ Heterostructures

TL;DR

This paper demonstrates a novel method to optically control valley polarization in WSe$_2$/CrI$_3$ heterostructures by tuning the magnetic exchange field through laser power, enabling efficient valley manipulation without large magnetic fields.

Contribution

It introduces a new approach to control valley pseudospins via optical tuning of magnetization in 2D heterostructures, expanding possibilities for valleytronic devices.

Findings

Achieved continuous tuning of valley polarization with laser power.

Demonstrated magnetic exchange field tuning over 20 T.

Enabled optical control of valley pseudospins in 2D heterostructures.

Abstract

Monolayer valley semiconductors, such as tungsten diselenide (WSe$_2$), possess valley pseudospin degrees of freedom that are optically addressable but degenerate in energy. Lifting the energy degeneracy by breaking time-reversal symmetry is vital for valley manipulation. This has been realized by directly applying magnetic fields or via pseudo-magnetic fields generated by intense circularly polarized optical pulses. However, sweeping large magnetic fields is impractical for devices, and the pseudo-magnetic fields are only effective in the presence of ultrafast laser pulses. The recent rise of two-dimensional (2D) magnets unlocks new approaches to control valley physics via van der Waals heterostructure engineering. Here we demonstrate wide continuous tuning of the valley polarization and valley Zeeman splitting with small changes in the laser excitation power in heterostructures formed by monolayer WSe$_2$ and 2D magnetic chromium triiodide (CrI$_3$). The valley manipulation is realized via optical control of the CrI$_3$magnetization, which tunes the magnetic exchange field over a range of 20 T. Our results reveal a convenient new path towards optical control of valley pseudospins and van der Waals magnetic heterostructures.