Magnetic Bulk Photovoltaic Effect in Bernal Bilayer Graphene

TL;DR

This study investigates how magnetic fields influence the bulk photovoltaic effect in Bernal bilayer graphene, revealing distinct behaviors of shift current and magnetic ballistic current under different magnetic conditions.

Contribution

It demonstrates the magnetic-field control of BPVE in bilayer graphene, highlighting the contrasting roles of edge states in shift current response under weak and strong magnetic fields.

Findings

Magnetic ballistic current grows linearly with weak magnetic fields.

Edge states are dark under weak fields but become bright contributors under strong fields.

Shift current responds mildly to weak magnetic fields.

Abstract

Magnetic fields break time-reversal symmetry (TRS) and reshape a material's spatial symmetry. Because the bulk photovoltaic effect (BPVE) is exquisitely sensitive to symmetry, it offers a natural arena for magnetic-field control. Here, we explore how shift current (SC) and magnetic ballistic current (MBC) evolve and emerge in AB-stacked Bernal bilayer graphene subjected to in-plane and out-of-plane magnetic fields. We find that the SC responds only mildly to weak fields, behaving as an almost even function of field strength. In contrast, the MBC is activated directly by TRS breaking and grows linearly with weak fields at selected photon energies. Focusing on AB-bilayer graphene ribbon we investigate the behavior of SC and MBC under both weak and strong vertical fields. We uncover the strikingly opposite roles played by edge states in the SC: under weak fields these highly localized, sublattice- and layer-polarized edge modes are essentially dark, yet under strong fields - when Landau levels dominate - the same edge states swell in spatial extent and become intensely bright contributors to the SC response.