Topological Phase Transition-Induced Triaxial Vector Magnetoresistance in (Bi_1–<i>x</i>In_<i>x</i>)₂Se₃ Nanodevices

We report the study of a triaxial vector magnetoresistance (MR) in nonmagnetic (Bi_1–<i>x</i>In_<i>x</i>)₂Se₃ nanodevices at the composition of <i>x</i> = 0.08. We show a dumbbell-shaped in-plane negative MR up to room temperature as well as a large out-of-plane positive MR. MR at three directions is about in a −3%:–1%:225% ratio at 2 K. Through both the thickness and composition-dependent magnetotransport measurements, we show that the in-plane negative MR is due to the topological phase transition enhanced intersurface coupling near the topological critical point. Our devices suggest the great potential for room-temperature spintronic applications in, for example, vector magnetic sensors