Helical spin thermoelectrics controlled by a side-coupled magnetic quantum dot in the quantum spin Hall state

Abstract

We study the thermoelectric response of a device containing a pair of helical edge states contacted at thesame temperature T and chemical potential μ and connected to an external reservoir, with different chemicalpotential and temperature, through a side quantum dot. Different operational modes can be induced by applyinga magnetic field B and a gate voltage Vg at the quantum dot. At finite B, the quantum dot acts simultaneously asa charge and a spin filter. Charge and spin currents are induced, not only through the quantum dot, but also alongthe edge states. We focus on linear response and analyze the regimes, which we identify as charge heat enginesor refrigerator, spin heat engine, and spin refrigerator.