Proximity-induced nonlinear magnetoresistances in topological insulators

We employ quadratic-response Kubo formulas to investigate the nonlinear magnetotransport in bilayers composed of a topological insulator and a magnetic insulator, and predict both unidirectional magnetoresistance and nonlinear planar Hall effects driven by interfacial disorder and spin-orbit scattering. These effects exhibit strong dependencies on the Fermi energy relative to the strength of the exchange interaction between the spin of Dirac electrons and the interfacial magnetization. In particular, as the Fermi energy becomes comparable to the exchange energy, the nonlinear magnetotransport coefficients can be greatly amplified and their dependencies on the magnetization orientation deviate significantly from conventional sinusoidal behavior. These findings may not only deepen our understanding of the origin of nonlinear magnetotransport in magnetic topological systems but also open new pathways to probe the Fermi and exchange energies via transport measurements.