Patent US 9,865,713

The interplay between chiral tunneling and spin-momentum locking of helical surface states leads to spin amplification and filtering in a 3D Topological Insulator (TI). Chiral tunneling across a TI pn junction allows normally incident electrons to transmit, while the rest are reflected with their spins flipped due to spin-momentum locking. The net result is that the spin current is enhanced while the dissipative charge current is simultaneously suppressed, leading to an extremely large, tunable longitudinal spin Hall angle (˜20) at the reflected end. At the transmitted end, the angle stays close to one and the electrons are completely spin polarized.