Light-Induced Hysteresis of Electronic Polarization in Anti-Ferromagnet FePS₃

Research on manipulating materials using light has garnered significant interest, yet examples of controlling electronic polarization in magnetic materials remain scarce. Here, the hysteresis of electronic polarization in the anti-ferromagnetic semiconductor FePS₃ is demonstrated via light. Below the Néel temperature, linear dichroism (i.e., optical anisotropy) without structural symmetry breaking is observed. Light-induced net polarization aligns along the a-axis (zigzag direction) at 1.6 eV due to the dipolar polarization and along the b-axis (armchair direction) at 2.0 eV due to the combined effects of dipolar and octupolar polarizations, resulting from charge transfer from the armchair to the zigzag direction by light. Unexpected hysteresis of the electronic polarization occurs at 2.0 eV due to the octupolar polarization, in contrast to the absence of such hysteresis at 1.6 eV. This is attributed to a symmetry breaking of the light-induced phase of FePS₃ involving electronic polarization within the spin lattice. Here a new mechanism is suggested for generating and controlling electronic polarization in magnetic materials using light, with implications for future device applications.