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 the same temperature T and chemical potential µ and connected to an external reservoir, with different chemical potential and temperature, through a side quantum dot. Different operational modes can be induced by applying a magnetic field B and a gate voltage Vg at the quantum dot. At finite B, the quantum dot acts simultaneously as a charge and a spin filter. Charge and spin currents are induced, not only through the quantum dot, but also along the edge states. We focus on linear response and analyze the regimes, which we identify as charge heat engines or refrigerator, spin heat engine and spin refrigerator.PACS numbers:

Thermoelectric cooling properties of a quantum Hall Corbino device

“…A significant amount of work has been published on thermoelectricity in quantum coherent systems. Paradigmatic examples are quantum dots [7][8][9][10][11][12][13][14][15][16], nanowires [17,18] quantum point contacts [19][20][21][22] and topological edge states of the quantum Hall and the quantum spin Hall regimes [23][24][25][26][27][28][29][30][31][32][33][34][35]. In these cases transport takes place through a few ballistic channels.…”

Interference effects induced by a precessing easy-plane magnet coupled to a helical edge state

“…Since backscattering of electrons in the helical edge of a two-dimensional topological insulator is forbidden by timereversal symmetry, breaking time-reversal symmetry by an applied magnetic field or by coupling of the helical edge to the exchange field of a magnet or a magnetic impurity is the only mechanism by which electrons in a helical edge can be backscattered. [1][2][3][4][5][6] The purposeful coupling of the helical edge to magnetic insulators has been shown to result in fascinating properties, such as the appearance of Majorana zero modes at the boundary between segments with a magnet-induced gap and with proximity-induced superconductivity, 7 various thermoelectric effects, 8,9 or the possibility to convert electrical energy to mechanical motion in an adiabatic quantum motor. 10,11 Magnetic impurities exchange-coupled to the helical edge states exhibit characteristic Kondo effects [12][13][14][15] and electrically controlled dynamics of the impurity spin due to backscattering of helical edge state electrons.…”

Signatures of Jackiw-Rebbi resonance in the thermal conductance of topological Josephson junctions with magnetic islands

“…The key role played by a magnetic island placed inside the 2DTI is to introduce a boundary with a backscattering process in the Dirac system constituted by the helical edge states. Without the superconducting ingredient, this phenomenon leads to interesting effects in the electron transport [28][29][30][31][32][33] and in thermoelectric [34][35][36] properties. The fact that the magnetic island may have multiple domains further extends the scenario to interesting topological structures.…”