Adiabatic quantum pumping through surface states in 3D topological insulators

TL;DR

This paper explores adiabatic quantum pumping of Dirac fermions on the surface of 3D topological insulators, analyzing different junction geometries and their conductance and pumped current behaviors.

Contribution

It introduces a detailed scattering matrix analysis of quantum pumping in topological insulator surface states with novel insights into resonant modes and current divergence.

Findings

Pumped current diverges at resonant transmission modes.

Oscillatory conductance explained by resonant conditions.

Distinguishable features between pumped and rectified currents.

Abstract

We investigate adiabatic quantum pumping of Dirac fermions on the surface of a strong 3D 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 first calculate the tunneling conductance and then the adiabatically pumped current using different pumping mechanisms for both types of junctions. We explain the oscillatory behavior of the conductance by studying the condition for resonant transmission in the junctions and find that each time a new resonant mode appears in the transport window, the pumped current diverges. We also predict an experimentally distinguishable difference between the pumped current and the rectified current.