Nonreciprocal charge transport at magnetic topological insulator interfaces

The surface state of a topological insulator has provided a simple yet effective platform for studying spin-orbit effects in quantum materials over the past decade. Especially, when the spin-momentum-locked electrons are coupled to a magnetic constituent, the electronic motion of the surface state is strongly influenced by the magnetization direction. One of the most representative examples is the quantum anomalous Hall effect, where unidirectional chiral edge mode appears at the edge of the sample due to spontaneous magnetization. In this talk, we will introduce another example of exotic transport in magnetic topological insulators: nonreciprocal charge transport, where the sample's resistance depends on the current direction [1]. Interestingly, we observe two types of nonreciprocal transport (also called unidirectional resistance) in Cr-doped (Bi,Sb)₂Te₃ in a different measurement configuration; in-plane and out-of-plane magnetization. Under in-plane magnetization, the interaction between the spin-momentum locked two-dimensional surface state and the in-plane magnetization gives sizable unidirectional resistance [2]. Meanwhile, in quantum anomalous Hall regime under out-of-plane magnetization, we observe a large nonreciprocal transport at the one-dimensional chiral edge state [3]. We will discuss the origin of these effects in detail. Nonreciprocal transport can be implemented in other topological materials such as quantum Hall states and magnetic Weyl semimetals to study the dissipation mechanism of the topological modes.
[1] Y. Tokura, N. Nagaosa, Nature Commun. 9, 3740 (2018).
[2] K. Yasuda et al., Phys. Rev. Lett. 117, 127202 (2016).
[3] K. Yasuda et al., Nature Nanotech. 15, 831–835 (2020).