Symmetry regimes for circular photocurrents in monolayer MoSe2

Jorge Quereda,Jeroen Van Den Brink,Caspar H Van Der Wal,Bart J Van Wees,Jhih-Shih You,Talieh S Ghiasi

doi:10.1038/s41467-018-05734-z

Abstract

In monolayer transition metal dichalcogenides helicity-dependent charge and spin photocurrents can emerge, even without applying any electrical bias, due to circular photogalvanic and photon drag effects. Exploiting such circular photocurrents (CPCs) in devices, however, requires better understanding of their behavior and physical origin. Here, we present symmetry, spectral, and electrical characteristics of CPC from excitonic interband transitions in a MoSe2 monolayer. The dependence on bias and gate voltages reveals two different CPC contributions, dominant at different voltages and with different dependence on illumination wavelength and incidence angles. We theoretically analyze symmetry requirements for effects that can yield CPC and compare these with the observed angular dependence and symmetries that occur for our device geometry. This reveals that the observed CPC effects require a reduced device symmetry, and that effects due to Berry curvature of the electronic states do not give a significant contribution.

Highlights

In monolayer transition metal dichalcogenides helicity-dependent charge and spin photocurrents can emerge, even without applying any electrical bias, due to circular photogalvanic and photon drag effects
In ref.[11] it was proposed that Berry curvature (BC) at the band edges of 1L-TMDCs can give a contribution to circular photocurrents (CPCs) (BC-induced circular photogalvanic effect (CPGE), BC-CPGE)
As we present in Supplementary Note 6, the device symmetries strongly constrain the tensor components, and they can still vanish for high-symmetry configurations, even for broken inversion symmetry

Summary

Introduction

In monolayer transition metal dichalcogenides helicity-dependent charge and spin photocurrents can emerge, even without applying any electrical bias, due to circular photogalvanic and photon drag effects. Exploiting such circular photocurrents (CPCs) in devices, requires better understanding of their behavior and physical origin. By testing the dependence of CPC on the light incident angle we find that it presents very different symmetry for the two regimes: for small Vds, the CPC is preserved when the incidence angle is switched from φ to –φ, whereas for large Vds, inverting the illumination angle φ causes a change of sign for the CPC, pointing to a separate physical origin. 1L-MoSe2 channel, one can tune the relative strength of the two contributions at a fixed drain-source voltage, achieving control over the intensity and direction of the helicity-dependent photoresponse

Methods

Results

Conclusion