Current-control of chiral orbital currents in a colossal magnetoresistance material

The ferrimagnetic insulator Mn₃Si₂Te₆ shows an unusual colossal magnetoresistance (CMR) where the electrical resistance is reduced by 7-order-of-magnitude. This CMR occurs only when a magnetic polarization is avoided, and defies all existing models and precedents [1,2]. Here we report an exotic quantum state that is driven by chiral orbital currents (COC) flowing along edges of MnTe₆ octahedra. The COC generates c-axis orbital moments of ab-plane COC that couple to the Mn spins. Application of magnetic fields along the magnetic hard c axis drastically enhances the COC with a certain circulation direction (i.e, either clockwise or counterclockwise), which in turn significantly reduces electron scattering, leading to the CMR. This COC-driven CMR and Hall effect are extraordinarily susceptible to small external currents exceeding a certain threshold. As a result, application of small DC currents leads to exotic time-dependent, bistable switching, which takes seconds or even minutes to occur [3]. This switching mimics a first-order "melting transition” from the COC-state to the trivial state. In this talk we present our recent results, particularly the Hall effect as a function of applied DC current.