Non-Reciprocity of the Wave Packet Scattering Delay in Ballistic Two-Terminal Devices

TL;DR

This paper reveals that in ballistic two-terminal devices, wave packet scattering delays are direction-dependent and break reciprocity, unlike transmission probabilities, especially when channel exchange symmetry is broken.

Contribution

It demonstrates the non-reciprocal nature of wave packet scattering delays in ballistic devices, highlighting a fundamental difference from transmission probabilities.

Findings

Wave packet delays are direction-dependent.

Reciprocity does not hold for scattering delays.

Breaking channel exchange symmetry causes non-reciprocity.

Abstract

In the linear regime, transport properties of ballistic two-terminal devices are generally considered to be independent of the direction of the current. This two-terminal reciprocity applies to both the electron transmission and reflection probabilities. However, it does not apply to the scattering delays of wave packets. Indeed, \emph{four} different time delays describe the transmission and reflection processes of wave packets arriving from the two terminals, respectively. Unlike the probabilities, these delays are direction dependent if the channel exchange symmetry of the scattering matrix is broken.