All-electrical near-field injection of excitons in a van der Waals antiferromagnet

TL;DR

This paper demonstrates the electrical excitation of excitons in CrSBr van der Waals layers using a graphene tunnel junction, enabling room-temperature electroluminescence and exciton polariton formation, advancing spintronic and photonic applications.

Contribution

It introduces a novel all-electrical method to excite excitons in CrSBr layers via tunneling electrons, including at room temperature, and observes exciton polaritons in thicker layers.

Findings

Electrically excited emission observed from bilayer to 250 nm thick CrSBr.

Strong linear polarization confirms excitonic origin of electroluminescence.

Evidence of exciton polaritons in thicker layers indicating strong light-matter coupling.

Abstract

Van der Waals materials have become a promising building block for future electronics and photonics. The two-dimensional magnet CrSBr came into the spotlight of solid state research due to its intriguing combination of antiferromagnetic order, strong light-matter coupling and unusual quasi-1D electronic bandstructure. This study reports the electrical excitation of excitons in CrSBr layers from cryogenic temperatures up to room temperature. By exploiting the energy transfer via tunneling electrons in a graphene tunnel junction strongly bound excitons are excited in proximate CrSBr layers. This facilitates electrically-excited emission from CrSBr crystals ranging in thickness from a bilayer up to 250 nm, in which the strong linear polarization of the electroluminescence confirms the excitonic origin. For thicker layers, clear evidence for the electrically excited emission from self-hybridized exciton polaritons is observed, highlighting the strong coupling between optical excitations and confined photon modes in CrSBr. These results pave the way for future applications in spintronic and optical readout of magnetic properties.