Se doping effect on metal-to-insulator transition in GdPS.

Topological materials have provided a great opportunity to fine-tune the topological states through element substitutions. One of the known parameters that affects electronic states which are easily tuned by elemental substitution is spin orbit coupling. GdPS, a magnetic member of the ZrSiS family, displays an insulator state owing to mirror symmetry breaking, which can be convert to a metal state through exchange splitting when application a magnetic field. Such field-driven insulator-to-metal transition that led to gigantic negative magnetoresistance, which is surprising isotropic originating from the minimized magnetic anisotropy due to vanishing spin-orbit coupling of the half-filled 4f electron configuration for Gd³⁺. Here we report the effect of Se substitution for S in GdPS, which is expected to enhance spin-orbit coupling and modify the magnetic anisotropy. The gigantic negative magnetoresistance and insulator-to-metal transition is found to be affected by Se substitution.