In a study published in ACS Applied Materials & Interfaces, researchers from the Changchun Institute of Optics, Fine Mechanics and Physics of the Chinese Academy of Sciences, and collaborators, demonstrated a novel method to generate spin-dependent electrical currents at room temperature by precisely controlling the symmetry at the interface between two atomically thin materials.

Using spatially resolved photocurrent mapping, researchers confirmed that the observed electrical current originated directly from the hexagonal boron nitride (hBN)/chromium thiophosphate (CrPS₄) interface and not from other effects like Schottky barriers at the metal contacts. 

They then probed the photogalvanic effect (PGE). Linearly polarized light tests revealed a shift current, one component of PGE, whose direction and strength depended predictably on the light's polarization angle. This behavior matched theoretical predictions for an interface with a single mirror plane.

Moreover, researchers made a test of circularly polarized light. Through symmetry analysis, they revealed that breaking the mirror symmetry lifted constraints on the Berry curvature distribution, allowing the formation of a Berry curvature dipole, which is responsible for converting the helicity of the circularly polarized light into a directional flow of spin-polarized electrons.

Second-harmonic generation measurements showed that the nonlinear optical response at the hBN/CrPS₄ interface differed significantly from the simple sum of individual layers' responses, which confirmed strong interfacial coupling and electronic interactions. This proved that the hBN layer actively modified the symmetry and electronic properties of the CrPS₄ at the interface.

This study highlights the critical role of interface symmetry breaking in inducing quantum geometric-related effects at magnetic material interfaces and provides a new method for manipulating interface Parity-Time symmetry.