Transport through a quantum spin Hall quantum dot

Quantum spin Hall insulators, recently realized in HgTe/(Hg,Cd)Te quantum wells, support topologically protected, linearly dispersing edge states with spin-momentum locking. A local magnetic exchange field can open a gap for the edge states. A quantum-dot structure consisting of two such magnetic tunneling barriers is proposed, and the charge transport through this device is analyzed. The effects of the bias voltage, the gate voltage, and the charging energy in the quantum dot are studied employing Landauer and master-equation approaches. For vanishing charging energy, the differential conductance is periodic in both gate and bias voltages. For nonzero charging energy, the periodicity in the gate voltage is retained, but with increased period. A partial recurrence of the noninteracting periodicities is found for strong interactions. The possibility of controlling the edge magnetization by a locally applied gate voltage is proposed.