Relativistic ratcheting on the surface of topological insulator Bi2Se3 attached to spiral multiferroic oxide.

Relativistic ratcheting of Dirac fermions on the surface of topological insulator Bi 2 Se 3 attached to a spiral multiferroic oxide is investigated. We find that the Dirac fermions on the surface of topological insulator Bi 2 Se 3 exhibit pronounced Brownian motion, tuned by the strength of exchange field established by the interaction of spin degrees of Dirac fermions and multiferroic oxide. The surface Dirac fermions show ratchet effect as a net current under the influence of orthogonal, commensurate ac drives in the presence of a symmetric periodic potential set by the exchange field. [ABSTRACT FROM AUTHOR]