Tunable geometric photocurrent in van der Waals heterostructure

Abstract

Utilizing the spin or valley degree of freedom is a promising approach for realizing more energy-efficient information processing devices. Circularly polarized light can be used to generate spin/valley current in monolayer 2D transition metal dichalcogenides. We observe a geometrically dependent photocurrent in heterostructure M o S 2 / W S e 2 , where light with a different circular polarization generates photocurrents in opposite directions. Furthermore, we show that this photocurrent persists even at room temperature, and it can be controlled using an in-plane electric field and back gating. We explain the observed phenomena via valley-dependent valence band shift and the valley optical selection rule. This finding may facilitate the use of 2D heterostructures as a platform for opto-valleytronics and opto-spintronics devices.

Self-Powered Filterless On-Chip Full-Stokes Polarimeter

“…24,26 Under illumination by a circularly polarized light with certain helicity, the resulting CPGE current is a superposition of electron current and hole current, which propagates along the same direction but with an opposite sign. 31,39 Therefore, electron current and hole current tend to cancel each other in each single valley. In this SL-MoS 2 /FL-MoS 2 homojunction, the band alignment enables holes to undergo ultrafast transfer from SL-MoS 2 to FL-MoS 2 due to the relatively large valence band offset between them, while electron transfer can be neglected.…”

“…24,26 Under illumination by a circularly polarized light with certain helicity, the resulting CPGE current is a superposition of electron current and hole current, which propagates along same direction but with an opposite sign. 31,38 Therefore, electron current and hole current tend to cancel each other in each single valley.…”

“…39 As a result, the hole current is significantly reduced and the net CPGE current in the homojunction mainly originates from electron current, which is thus greatly enhanced in such SL-MoS 2 /FL-MoS 2 homojunction, similar to that in a MoS 2 /WSe 2 heterostructure. 31 In addition, the built-in electric field in such homojunction would also expect to contribute to the enhanced CPGE current. 27,28…”

“…29−31 A recent study reveals that obvious CPGE current has been observed in MoS 2 /WSe 2 heterojunction under normal incidence, confirming the modulation effect of van der Waals junctions on the CPGE current. 31 In this sense, it is feasible to detect all SOP of light in a SL TMDC based van der Waals junction by utilizing its CPGE effect and intrinsic optical anisotropy between in-plane and out-of-plane directions. Here, we have successfully demonstrated a self-powered filterless on-chip full-Stokes polarimeter in a SL-MoS 2 /few-layer MoS 2 (FL-MoS 2 ) homojunction by using the built-in electric field enhanced CPGE current and the linearly polarized photoresponse between in-plane and out-ofplane of MoS 2 .…”

Exchange coupling–mediated broken symmetries in Ta 2 NiSe 5 revealed from quadrupolar circular photogalvanic effect

“…S8). This is in contrast to electric dipole-induced bias-dependent CPGE, which typically gets modulated proportional to the electric-field strength that aids in symmetry breaking (31,42). Joule heating of the device beyond the transition temperature T c = 323 K can be ruled out as the heat required to raise the temperature of a typical device by 30 K is at least two orders of magnitude more than the heat generated by resistive heating at the 200-mV bias (see fig.…”