Generation, transport, and detection of valley-locked spin photocurrent in WSe2-graphene–Bi2Se3 heterostructures

Abstract

Quantum optoelectronic devices capable of isolating a tar-get degree of freedom (DoF) from other DoFs have allowed for new applications in modern information technology. Many works on solid-state spintronics have focused on methods to disentangle the spin DoF from the charge DoF1, yet many related issues remain unresolved. Although the recent advent of atomically thin transition metal dichalcogenides (TMDs) has enabled the use of valley pseudospin as an alternative DoF2,3, it is nontrivial to separate the spin DoF from the valley DoF since the time-reversal valley DoF is intrinsically locked with the spin DoF4. Here, we demonstrate lateral TMD?밽ra-phene?뱓opological insulator hetero-devices with the possibil-ity of such a DoF-selective measurement. We generate the valley-locked spin DoF via a circular photogalvanic effect in an electric-double-layer WSe2 transistor. The valley-locked spin photocarriers then diffuse in a submicrometre-long gra-phene layer, and the spin DoF is measured separately in the topological insulator via non-local electrical detection using the characteristic spin?뱈omentum locking. Operating at room temperature, our integrated devices exhibit a non-local spin polarization degree of higher than 0.5, providing the potential for coupled opto-spin?뱕alleytronic applications that indepen-dently exploit the valley and spin DoFs.