Bulk photogalvanic current control and gap spectroscopy in 2D hexagonal materials

Abstract

Two-dimensional (2D) hexagonal materials have been intensively explored for multiple optoelectronic applications such as spin current generation, all-optical valleytronics, and topological electronics. In the realm of strong-field and ultrafast light-driven phenomena, it was shown that tailored laser driving such as polychromatic or few-cycle pulses can drive robust bulk photogalvanic (BPG) currents originating from the K/K′ valleys. We here explore the BPG effect in 2D systems in the strong-field regime and show that monochromatic elliptical pulses also generically generate such photocurrents. The resultant photocurrents exhibit both parallel and transverse (Hall-like) components, both highly sensitive to the laser parameters, providing photocurrent control knobs. Interestingly, we show that the photocurrent amplitude has a distinct behavior vs. the driving ellipticity that can be indicative of material properties such as the gap size at K/K′, which should prove useful for novel forms of BPG-based spectroscopies. We demonstrate these effects also in benchmark ab initio simulations in monolayer hexagonal boron–nitride. Our work establishes new paths for controlling photocurrent responses in 2D systems that can also be used for multi-dimensional spectroscopy of ultrafast material properties through photocurrent measurements.