arXiv subjects

Matteo Acciai

Publications and source records attributed to Matteo Acciai.

22 records · Page 2Linked to original sources

arXiv2019

Levitons in superconducting point contacts

We investigate the transport properties of a superconducting quantum point contact in the presence of an arbitrary periodic drive. In particular, we calculate the dc current and noise in the tunnel limit, obtaining general expressions in terms of photoassisted probabilities. Interesting features can be observed when the frequency is comparable to the gap. Here, we show that quantized Lorentzian pulses minimize the excess noise, further strengthening the hierarchy among different periodic drives observed in the electron quantum optics domain. In this regime, the excess noise is directly connected to the overlap between electron and hole energy distributions driven out of equilibrium by the applied voltage. In the adiabatic limit, where the frequency of the drive is very small compared to the superconducting gap, we recover the conventional Shapiro-spikes physics in the supercurrent.

cond-mat.mes-hall↗

arXiv2018

Probing interactions via non-equilibrium momentum distribution and noise in integer quantum Hall systems at $ν=2$

We consider the excitation of single-electron wave packets by means of a time dependent voltage applied to the ballistic edge channels of the integer quantum Hall effect at filling factor $ν=2$. Due to electron-electron interactions, fractional excitations emerge along the edge. Their detailed structure is analyzed by evaluating the nonequilibrium momentum distributions associated with the different edge channels. We provide results for a generic time-dependent drive both in the stationary regime and for intermediate times, where the overlap between fractionalized wave packets carries relevant information on interaction strength. As a particular example we focus on a Lorentzian drive, which provides a clear signature of the minimal excitations known as Levitons. Here, we argue that inner-channel fractionalized excitations can be exploited to extract information about inter-channel interactions. We further confirm this idea by calculating the zero frequency noise due to the partitioning of these excitations at a quantum point contact and we propose a measurable quantity as a tool to directly probe electron-electron interactions and determine the so-called mixing angle of copropagating quantum Hall channels.

cond-mat.mes-hall↗

arXiv2017

Charge and energy fractionalization mechanism in one-dimensional channels

We study the problem of injecting single electrons into interacting one-dimensional quantum systems, a fundamental building block for electron quantum optics. It is well known that such injection leads to charge and energy fractionalization. We elucidate this concept by calculating the nonequilibrium electron distribution function in the momentum and energy domains after the injection of an energy-resolved electron. Our results shed light on how fractionalization occurs via the creation of particle-hole pairs by the injected electron. In particular, we focus on systems with a pair of counterpropagating channels, and we fully analyze the properties of each chiral fractional excitation which is created by the injection. We suggest possible routes to access their energy and momentum distribution functions in topological quantum Hall or quantum spin-Hall edge states.

cond-mat.mes-hall↗

arXiv2016

Time-resolved energy dynamics after single electron injection into an interacting helical liquid

The possibility to inject a single electron into ballistic conductors is at the basis of the new field of electron quantum optics. Here, we consider a single electron injection into the helical edge channels of a topological insulator. Their counterpropagating nature and the unavoidable presence of electron-electron interactions dramatically affect the time evolution of the single wavepacket. Modeling the injection process from a mesoscopic capacitor in presence of non-local tunneling, we focus on the time resolved charge and energy packet dynamics. Both quantities split up into counterpropagating contributions whose profiles are strongly affected by the interactions strength. In addition, stronger signatures are found for the injected energy, which is also affected by the finite width of the tunneling region. Indeed, the energy flow can be controlled by tuning the injection parameters and we demonstrate that, in presence of non-local tunneling, it is possible to achieve situation in which charge and energy flow in opposite directions.

cond-mat.mes-hall↗