Non-vanishing Berry phase in chiral insulators

Abstract

The binary compounds FeSi, RuSi, and OsSi are chiral insulators crystallizing in the space group P213 which is cubic. By means of ab initio calculations we find for these compounds a non-vanishing electronic Berry phase, the sign of which depends on the handedness of the crystal. There is thus the possibility that the Berry phase signals the existence of a macroscopic electric polarization due to the electrons. We show that this is indeed so if a small external magnetic field is applied in the [111] direction. The electric polarization is oscillatory in the magnetic field and possesses a signature that distinguishes the handedness of the crystal. Our findings add to the discussion of topological classifications of insulators and are significant for spintronics applications, and in particular, for a deeper understanding of skyrmions in insulators.