Bulk rectification effect in a polar semiconductor

Electrical rectification is usually achieved by layering p-type and n-type materials, but experiments now demonstrate rectification in a bulk polar semiconductor that has inversion-symmetry breaking and strong Rashba spin–orbit coupling. Noncentrosymmetric conductors are an interesting material platform, with rich spintronic functionalities 1 , 2 and exotic superconducting properties 3 , 4 typically produced in polar systems with Rashba-type spin–orbit interactions 5 . Polar conductors should also exhibit inherent nonreciprocal transport 6 , 7 , 8 , in which the rightward and leftward currents differ from each other. But such a rectification is difficult to achieve in bulk materials because, unlike the translationally asymmetric p–n junctions, bulk materials are translationally symmetric, making this phenomenon highly nontrivial. Here we report a bulk rectification effect in a three-dimensional Rashba-type polar semiconductor BiTeBr. Experimentally observed nonreciprocal electric signals are quantitatively explained by theoretical calculations based on the Boltzmann equation considering the giant Rashba spin–orbit coupling. The present result offers a microscopic understanding of the bulk rectification effect intrinsic to polar conductors as well as a simple electrical means to estimate the spin–orbit parameter in a variety of noncentrosymmetric systems.