Modulated currents in open nanostructures

TL;DR

This paper theoretically analyzes how modulated currents behave in open nanostructures like quantum dots and wires under pulsed input, revealing how spectral properties influence transient transport and signal delay.

Contribution

It introduces a non-Markovian master equation approach to study time-dependent transport in mesoscopic systems with pulsed driving, highlighting the role of spectral states and bias window effects.

Findings

Output current depends on lead-sample coupling, pulse length, and propagating states.

Increasing bias window introduces additional transport structures due to new states.

Signal delay in quantum wire linked to transient time through the wire.

Abstract

We investigate theoretically the transport properties of a mesoscopic system driven by a sequence of rectangular pulses applied at the contact to the input (left) lead. The characteristics of the current which would be measured in the output (right) lead are discussed in relation with the spectral properties of the sample. The time-dependent currents are calculated via a generalized non-Markovian master equation scheme. We study the transient response of a quantum dot and of a narrow quantum wire. We show that the output response depends not only on the lead-sample coupling and on the length of the pulse but also on the states that propagate the input signal. We find that by increasing the bias window the new states available for transport induce additional structure in the relaxation current due to different dynamical tunneling processes. The delay of the output signal with respect to the input current in the case of the narrow quantum wire is associated to the transient time through the wire.