Colossal angular magnetoresistance in a ferrimagnetic nodal-line semiconductor Mn₃Si₂Te₆

Topological magnets, where both magnetism and nontrivial band topology coexist, have emerged as promising candidates to realize novel electronic and spintronic functionalities, because their topological band degeneracy can be readily tuned by spin configurations, thus dramatically modulating electronic conduction. Here we propose a new class of topological magnets, namely, magnetic nodal-line semiconductors, in which spin-polarized conduction or valence bands possess topological nodal-line degeneracy. Taking a layered ferrimagnet Mn₃Si₂Te₆ as a model system, we show that the topological band degeneracy, driven by chiral molecular orbital states, is lifted depending on the spin orientation, which leads to a metal-insulator transition in the same ferrimagnetic phase. As a result, we have observed extremely large angular magnetoresistance exceeding a trillion percent per radian, which we call colossal angular magnetoresistance. Our findings highlight that magnetic nodal-line semiconductors are a promising platform for realizing extremely sensitive spin- or orbital-dependent functionalities.