Adiabatic quantum pumping through surface states in 3D topological insulators

We investigate adiabatic quantum pumping of ballistic Dirac fermions on the surface of a strong three-dimensional topological insulator. Two different geometries are studied in detail, a normal metal–ferromagnetic–normal metal (NFN) junction and a ferromagnetic–normal metal–ferromagnetic (FNF) junction. Using a scattering matrix approach, we show that each time a new resonant mode appears in the transport window the pumped current exhibits a maximum and provide a detailed analysis of the position of these maxima. We also predict a characteristic difference between the pumped current in NFN- and FNF-junctions: whereas the former vanishes for carriers at normal incidence, the latter is finite due to the different nature of wavefunction interference in the junctions. Finally, we predict an experimentally distinguishable difference between the pumped current and the conductance.Quantum NanoscienceApplied Science