Giant Valley-Zeeman Splitting from Spin-Singlet and Spin-Triplet Interlayer Excitons in WSe2/MoSe2 Heterostructure

TL;DR

This study identifies and characterizes spin-singlet and spin-triplet interlayer excitons in WSe2/MoSe2 heterostructures, revealing giant valley-Zeeman splitting and high valley polarization, advancing potential spintronics and valleytronics applications.

Contribution

First unambiguous identification of spin-singlet and spin-triplet interlayer excitons in WSe2/MoSe2 heterostructures with detailed spectroscopic analysis.

Findings

Giant valley-Zeeman splitting with g-factors ~10.7 and ~15.2.

Opposite helicities of PL from singlet and triplet excitons.

High valley polarization approaching unity at low temperature.

Abstract

Transition metal dichalcogenides (TMDCs) heterostructure with a type II alignment hosts unique interlayer excitons with the possibility of spin-triplet and spin-singlet states. However, the associated spectroscopy signatures remain elusive, strongly hindering the understanding of the Moire potential modulation of the interlayer exciton. In this work, we unambiguously identify the spin-singlet and spin-triplet interlayer excitons in the WSe2/MoSe2 hetero-bilayer with a 60-degree twist angle through the gate- and magnetic field-dependent photoluminescence spectroscopy. Both the singlet and triplet interlayer excitons show giant valley-Zeeman splitting between the K and K' valleys, a result of the large Lande g-factor of the singlet interlayer exciton and triplet interlayer exciton, which are experimentally determined to be ~ 10.7 and ~ 15.2, respectively, in good agreement with theoretical expectation. The PL from the singlet and triplet interlayer excitons show opposite helicities, determined by the atomic registry. Helicity-resolved photoluminescence excitation (PLE) spectroscopy study shows that both singlet and triplet interlayer excitons are highly valley-polarized at the resonant excitation, with the valley polarization of the singlet interlayer exciton approaches unity at ~ 20 K. The highly valley-polarized singlet and triplet interlayer excitons with giant valley-Zeeman splitting inspire future applications in spintronics and valleytronics.