Spin-selective magneto-conductivity in WSe$_2$

Material systems that exhibit tunable spin-selective conductivity are key components of spintronic technologies. Here we demonstrate a novel type of spin-selective transport, based on the unusual Landau level (LL) sequence observed in bilayer WSe$_2$ under large applied magnetic fields. We find that the conductivity depends strongly on the relative iso-spin ordering between conducting electrons in a partially filled LL and the localized electrons of lower energy filled LLs, with conductivity observed to be almost completely suppressed when the spin-ratio and field-tuned Coulomb energy exceed a critical threshold. Switching between "on/off" states is achievable through either modulation of the external magnetic or electric fields, with many-body interaction driving a collective switching mechanism. In contrast to magnetoresistive heterostructures, this system achieves electrically tunable spin filtering within a single material, driven by interaction between free and localized spins residing in energy-separated spin/valley polarized bands. Similar spin-selective conductivity may be realizable in multi-flat band systems at zero magnetic field.