Valley contrasting bulk photovoltaic effect in antiferromagnetic MnPSe$_3$ monolayer

TL;DR

This paper theoretically demonstrates a sizable valley contrasting bulk photovoltaic effect in antiferromagnetic MnPSe3 monolayer, revealing hidden valley-polarized photoconductivity and potential for future opto-spintronic devices.

Contribution

It introduces the concept of valley contrasting BPV effect in a PT-symmetric 2D antiferromagnetic semiconductor, showing control via the Neel vector and predicting observable valley-polarized photoconductivity.

Findings

Valley contrasting BPV effect can emerge even when total photocurrent is forbidden.

Hidden valley-polarized photoconductivity could reach 1350 μA/V².

MnPSe3 monolayer may be two-dimensional ferrotoroidic, controllable by Neel vector.

Abstract

Valleytronics that uses the inequivalent electronic states at the band extrema in semiconductors have been considered to play a vital role in the future information read/write technology. In the current work, we theoretically show that sizable valley contrasting bulk photovoltaic (BPV) effect could emerge, even when the total photocurrent is symmetrically forbidden. We illustrate our theory by using a prototypical two-dimensional antiferromagnetic semiconductor, MnPSe3 monolayer, that is PT-symmetric (P and T refer to spatially inversion and time-reversal operators, respectively). We show that the Neel vector well controls the magnetic point group at the $\Gamma$ point, and the BPV current direction. In addition, $\mathbf{k}$-dependent photocurrent generally arises due to the reduction of little group constraints at the valley. This leads to hidden valley-polarized photoconductivity which could reach a magnitude of 1350 $\mu$A/V&^2&, observable experimentally. We further predict that the MnPSe$_3$ monolayer could be two-dimensional ferrotoroidic, again depending on its Neel vector direction, which can be determined via magnetoelectric response measurements. Our work provides an exemplary platform for paving the route to future opto-spintronic and opto-valleytronic devices in a single antiferromagnetic nanomaterial.