Magnetic Field‐Insensitive and Temperature‐Robust Spin‐Valley Relaxation in h‐BN Encapsulated Monolayer MoS2

Abstract

While conventional understanding holds that electron spin‐valley relaxation in monolayer MoS2 is highly sensitive to weak transverse magnetic fields and thermal activation, the research reveals a different scenario when monolayer MoS2 is encapsulated in hexagonal boron nitride (h‐BN). Using time‐resolved Faraday rotation spectroscopy, it is found that the spin‐valley dynamics in h‐BN encapsulated monolayer MoS2 are independent of transverse magnetic fields and only weakly dependent on temperature. Notably, the spin‐valley polarization in h‐BN encapsulated monolayer MoS2 remains robust even at room temperature, exhibiting a biphasic behavior with lifetimes of 23 and 146 ps, attributed to itinerant electrons and trions, respectively. The study also clarifies the origin of the previously reported magnetic field‐sensitive spin‐valley component in monolayer MoS2, demonstrating that it likely originates from localized states rather than itinerant electrons and is absent in h‐BN encapsulated MoS2. These findings not only update the understanding of spin‐valley relaxation in monolayer MoS2 but also provide insights into the complexity and diversity of spin‐valley relaxation phenomena in monolayer transition metal dichalcogenides.