Observation of magnetically switchable quantum geometric photocurrents with Liang Wu

In non-centrosymmetric materials, light can be rectified into two types of DC photocurrents, known as injection and shift currents, through the bulk photovoltaic effect. Recent theory has uncovered their deep relation with the two-state quantum geometry of resonant transitions: In non-magnetic crystals, where these currents have been routinely observed, the injection current responds to circular light and probes the Berry curvature, while the shift current responds to linear light and probes the geometric connection. Magnetic crystals have been predicted to show a new set of hitherto unobserved magnetically switchable photocurrents, with the roles of linear and circular light interchanged: A linear injection current, which probes the quantum metric, and circular shift current, which probes the geometric torsion. In my talk, I will present the existence of such currents in the van der Waals antiferromagnet, demonstrating the switching of the current by flipping the Néel vector. Furthermore, their specific frequency and temperature dependence confirms the assignment of circular shift and linear injection currents. Our work demonstrates a new way to control photocurrents in magnets that are directly tied to geometry and have promising applications in antiferromagnetic spintronics and light harvesting.

This lecture was made possible by the William C. Ferguson Fund.