Giant odd-parity magnetoresistance in a topological material / ferromagnet bilayer heterostructure*

Magnetoresistance (MR) is usually an even function of magnetic field (B) as described by Onsager reciprocal relation. However, it was recently found that MR can be an odd function of B, called odd-parity MR (OMR), in some materials with broken time reversal symmetry (TRS). However, OMR magnitudes reported thus far were too small (< 1%) for realistic applications. In this study, we have discovered giant OMR as large as 2000% in a bilayer heterostructure consisting of topological Dirac semimetal α-Sn (~ 3 nm) / ferromagnetic semiconductor (In_1-x,Fe_x)Sb (x = 14%, T_C = 300 K) grown by molecular beam epitaxy. The OMR reaches maximum when B is applied parallel to the current, excluding the contribution of Hall effects as a possible origin. When rotating the direction of B, angular dependence of the OMR is well explained by a model that takes into account a tilt term in the Weyl Hamiltonian induced by the TRS breaking [1]. This model is also consistent with our other findings such as TRS breaking indicated by the hysteresis in magnetoresistance, presence of linear-dispersion band components by Shubnikov-de Haas oscillations, and band structure predicted by our first-principles calculation. Our result will be promising for realistic applications of OMR to unidirectional magnetic sensors.

[1] A. Kundu, et al., New J. Phys. 22, 083081 (2020).