Spin-thermoelectric transport induced by interactions and spin-flip processes in two-dimensional topological insulators

Abstract

We consider thermoelectric transport properties of the edge states of a two-dimensional topological insulator in a double quantum point contact geometry coupled to two thermally biased reservoirs. Both spin-preserving and spin-flipping tunneling processes between opposite edges are analyzed in the presence of electron-electron interactions. We demonstrate that the simultaneous presence of spin-flipping processes and interactions gives rise to a finite longitudinal spin current. Moreover, its sign and amplitude can be tuned by means of gate voltages with the possibility to generate a pure spin current, with a vanishing charge current

Polarized heat current generated by quantum pumping in two-dimensional topological insulators

“…It is worth noting that in this work we restrict the analysis to the range of interaction strengths given 115412-2 by 1/ √ 3 K 1, for which it is possible to show that single electron tunneling is the dominant process (in the renormalization group sense), both in single and double QPC geometry [57,65,73,74].…”

“…(12) corresponds to the net amount of heat flow exchanged between the R channel and L channel due to backscattering processes and it does not give any information on the heat which locally enters into each reservoir separately. Using the standard perturbative approach [4,65,72,85] in the tunneling Hamiltonian, the average pumped currents can be calculated. At the lowest order in the tunneling one has the finite temperature currents (here, ν = n,q for particle-number and heat contributions)…”

“…Experimental evidence of 2D TIs was reported in CdTe/HgTe [59] and InAs/GaSb [60,61] quantum wells and has been predicted for a large class of new materials which relies on the presence of strong spin-orbit coupling [62][63][64]. These systems constitute an interesting playground to study coherent heat transport in which the spin degree of freedom can play a nontrivial role [31,65]. Moreover, the unavoidable presence of e-e interactions in helical edge states [53,[66][67][68][69] can dramatically affect the dynamics and have important consequences on thermal transport properties [65].…”

“…These systems constitute an interesting playground to study coherent heat transport in which the spin degree of freedom can play a nontrivial role [31,65]. Moreover, the unavoidable presence of e-e interactions in helical edge states [53,[66][67][68][69] can dramatically affect the dynamics and have important consequences on thermal transport properties [65].…”

Transport in quantum spin Hall edges in contact to a quantum dot

“…[16][17][18][19][20][21][22][23][24][25][26][27] Quantum interference is generated when tunneling processes between different Kramers pairs at opposite sides of the bar take place. The usual process is tunneling preserving spin, but the scenario is much richer when the tunneling with spin-flip also happens.…”