Optical Mapping of Spin/Valley Diffusion and Drift in Transition Metal Dichalcogenides

Transition Metal Dichalcogenides (TMDs) have garnered attention due to their potential for future spintronic applications. With the recent observations of long spin lifetimes and optical manipulation and detection of spins, the interest in this family of materials has only increased. However, an understanding of the spin/valley transport in these materials is crucial for most spintronic applications. In TMDs, spin/valley transport will be influenced by their strong spin-orbit coupling and Berry curvature, in addition to any inhomogeneities.
To investigate spin/valley transport in TMDs, we have developed a time-resolved Kerr rotation microscope which can independently move the pump and probe beams, allowing us to pump spins in one location and detect them in another location. With ~1 um spatial resolution and 150 fs temporal resolution, this allows unprecedented observation of spin/valley transport in TMDs. The optical set-up accounts for temporal corrections due to spatial differences between the beams, and allows the imaging of spins/valleys as they move away from their excitation source. Spin diffusion in TMDs is investigated at both different time and length scales. Applying a bias voltage allows us to investigate spin drift and effects of Berry curvature.