Unconventional isotropic in-plane Hall and MR response in Bi₂Se₃/EuS bilayer system

Proximity effects on topological insulator/magnetic insulator (TI/MI) bilayers intrigue the scientific community due to exotic ground states that emerge by locally lifting the ground state degeneracy [1]. In this talk, we present in-plane magnetic field study on a Bi₂Se₃ (TI)/EuS (MI) bilayer device where magnetic exchange coupling is one-sided and acting only on the top surface state [2,3]. Our magneto-transport study reveals longitudinal magnetoresistance (LMR) and planar Hall resistance (PHR) which exhibit a sharp switch in resistance at magnetic field < coercive field and symmetric about B=0 suggesting it's nontrivial topological origin. This effect is isotropic w.r.t azimuthal angle rotation of in-plane field and the effect persists in temperature regime T < 4K. A plausible mechanism that includes symmetry breaking by proximity exchange interaction on the surface states will be presented.
[1] M. Z. Hasan & C. L. Kane. Rev. Mod. Phys. 82, 3045–3067 (2010).
[2] P. Wei et al. Phys. Rev. Lett. 110, 186807 (2013).
[3] S. Mathimalar et al. npj Quantum Mater. 5, 64 (2020).