11 research outputs found
Polarized heat current generated by quantum pumping in two-dimensional topological insulators
We consider transport properties of a two dimensional topological insulator
in a double quantum point contact geometry in presence of a time-dependent
external field. In the proposed setup an external gate is placed above a single
constriction and it couples only with electrons belonging to the top edge. This
asymmetric configuration and the presence of an ac signal allow for a quantum
pumping mechanism, which, in turn, can generate finite heat and charge currents
in an unbiased device configuration. A microscopic model for the coupling with
the external time-dependent gate potential is developed and the induced finite
heat and charge currents are investigated. We demonstrate that in the
non-interacting case, heat flow is associated with a single spin component, due
to the helical nature of the edge states, and therefore a finite and polarized
heat current is obtained in this configuration. The presence of e-e
interchannel interactions strongly affects the current signal, lowering the
degree of polarization of the system. Finally, we also show that separate heat
and charge flows can be achieved, varying the amplitude of the external gate.Comment: 13 pages, 5 figure
The finite width of anyons changes their braiding signature
International audienceAnyons are particles intermediate between fermions and bosons, characterized by a nontrivial exchange phase, yielding remarkable braiding statistics. Recent experiments have shown that anyonic braiding has observable consequences on edge transport in the fractional quantum Hall effect (FQHE). Here, we study transport signatures of anyonic braiding when the anyons have a finite temporal width. We show that the width of the anyons, even extremely small, can have a tremendous impact on transport properties and braiding signatures. In particular, we find that taking the finite width into account allows us to explain recent experimental results on FQHE at filling factor [Ruelle et al., Phys. Rev. X , 011031 (2023)]. Our work shows that the finite width of anyons crucially influences setups involving anyonic braiding, especially for composite fractions where the exchange phase is larger than
Enhancing photon squeezing one Leviton at a time
International audienceA mesoscopic device in the simple tunnel junction or quantum point contact geometry emits microwaves with remarkable quantum properties, when subjected to a sinusoidal drive in the GHz range. In particular, single and two-photon squeezing as well as entanglement in the frequency domain have been reported. By revising the photo-assisted noise analysis developed in the framework of electron quantum optics, we present a detailed comparison between the cosine drive case and other experimentally relavent periodic voltages such as rectangular and Lorentzian pulses. We show that the latter drive is the best candidate in order to enhance quantum features and purity of the outgoing single and two-photon states, a noteworthy result in a quantum information perspective
Symmetry properties of mixed and heat photo-assisted noise in the quantum hall regime
We investigate the photo-assisted charge-heat mixed noise and the heat noise generated by periodic drives in Quantum Hall states belonging to the Laughlin sequence. Fluctuations of the charge and heat currents are due to weak backscattering induced in a quantum point contact geometry and are evaluated at the lowest order in the tunneling amplitude. Focusing on the cases of a cosine and Lorentzian periodic drive, we show that the different symmetries of the photo-assisted tunneling amplitudes strongly affect the overall profile of these quantities as a function of the AC and DC voltage contributions, which can be tuned independently in experiments
Crystallization of levitons in the fractional quantum Hall regime
Using a periodic train of Lorentzian voltage pulses, which generates
soliton-like electronic excitations called Levitons, we investigate the charge
density backscattered off a quantum point contact in the fractional quantum
Hall regime. We find a regular pattern of peaks and valleys, reminiscent of
analogous self-organization recently observed for optical solitons in
non-linear environments. This crystallization phenomenon is confirmed by
additional side dips in the Hong-Ou-Mandel noise, a feature that can be
observed in nowadays electron quantum optics experiments.Comment: 9 pages, 4 figure