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. 2019 Jan 23;11(3):3334-3341.
doi: 10.1021/acsami.8b17476. Epub 2019 Jan 8.

Electrical Control of Circular Photogalvanic Spin-Valley Photocurrent in a Monolayer Semiconductor

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Electrical Control of Circular Photogalvanic Spin-Valley Photocurrent in a Monolayer Semiconductor

Lei Liu et al. ACS Appl Mater Interfaces. .

Abstract

In a monolayer transition metal dichalcogenide (TMDC) that lacks structural inversion symmetry, spin degeneracy is lifted by strong spin-orbit coupling, and a distinctive spin-valley locking allows for the creation of valley-locked spin-polarized carriers with a circularly polarized optical excitation. When excited carriers also have net in-plane momentum, spin-polarized photocurrents can be generated at ambient temperature without magnetic fields or materials. The behavior of these spin-polarized photocurrents in monolayer TMDC remains largely unexplored. In this work, we demonstrate the tuning of spin-valley photocurrent generated from the circularly polarized photogalvanic effect in monolayer MoS2, including magnitude and polarization degree, by purely electric means at room temperature. The magnitude of spin-polarized photocurrent can be modulated up to 45 times larger, and the polarization degree of the total photocurrent can be tuned significantly (here from 0.5 to 16.6%) by gate control. Combined with the atomic thickness and wafer-scale growth capabilities of monolayer TMDC, the efficient electrical tuning of spin-valley photocurrent suggests a pathway to achieve spin-logic processing by local gate architectures in monolayer opto-spintronic devices.

Keywords: circular photogalvanic effect; electrostatic screening; gate control; monolayer transition metal dichalcogenide; spin-valley photocurrent.

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