Levitons in helical liquids with Rashba spin-orbit coupling probed by a superconducting contact

Abstract

We consider transport properties of a single edge of a two-dimensional topological insulators, in presence of Rashba spin-orbit coupling, driven by two external time-dependent voltages and connected to a thin superconductor. We focus on the case of a train of Lorentzian-shaped pulses, which are known to generate coherent single-electron excitations in two-dimensional electron gas, and prove that they are minimal excitations for charge transport also in helical edge states, even in the presence of spin-orbit interaction. Importantly, these properties of Lorentzian-shaped pulses can be tested computing charge noise generated by the scattering of particles at the thin superconductor. This represents a novel setup where electron quantum optics experiments with helical states can be implemented, with the superconducting contact as an effective beamsplitter. By elaborating on this configuration, we also evaluate charge noise in a collisional Hong-Ou-Mandel configuration, showing that, due to the peculiar effects induced by Rashba interaction, a non-vanishing dip at zero delay appears.

Influence of channel mixing in fermionic Hong-Ou-Mandel experiments

“…Then, it is clear that in the presence of mixing and if channels propagate with different velocities v 1 = v 2 , it is not possible to synchronize all arrival times at the QPC and this results in a never vanishing noise. Clearly, the amount by which the HOM dip is reduced depends both on the difference in the time delays (51), but also on the mixing strength that modifies the relative weight of the three terms in Eq. ( 50).…”

“…Several theoretical works [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] have investigated various properties of single-electron sources in this regime, and many experimental results [27][28][29][30][31][32][33][34][35][36][37][38] have shown that a high degree of control in the manipulation of single-electron excitations can be achieved. Moreover, extensions to interacting systems [39][40][41][42][43][44][45][46][47][48][49][50][51] have also been considered. In particular, the fractional quantum Hall regime plays a special role, due to the presence of fractionally charged quasiparticles, whose anyonic statistics can in principle be probed by electron quantum optics setups.…”

Rashba-controlled thermal valve in helical liquids

“…A specific and promising property of the systems just mentioned is that the strong SOC allows for the manipulation of a Rashba-like contribution [27][28][29][30] . To this end, external electric fields, induced for example by properly patterned side or top gates, can be used.…”

Spectral features of voltage pulses in interacting helical channels

“…Even though the majority of EQO experiments have been performed on integer quantum Hall systems [2], proposals aiming at extending the domain of EQO to other settings have been put forward. They include the fractional quantum Hall regime [28,29], where experimental efforts are in progress [49], superconducting systems [50,51], and 2DTIs [52][53][54][55][56][57][58][59][60], a context in which the recent implementation of quantum point contacts [61] is very promising for achieving interferometric setups.…”