How backscattering off a point impurity can enhance the current and make the conductance greater than e^2/h per channel

TL;DR

This paper investigates how a time-dependent impurity in a one-dimensional quantum wire can enhance conductance beyond the standard quantum limit, especially under strong interactions, challenging traditional expectations about backscattering effects.

Contribution

It demonstrates that a time-dependent impurity can increase conductance above e^2/h in a strongly interacting one-dimensional system, a novel effect not seen with static impurities.

Findings

Backscattering can enhance conductance under strong interactions.

Conductance exceeds e^2/h with a time-dependent impurity at g<1/2.

Potential experimental setups include quantum wires and Hall bars at fractional filling factors.

Abstract

It is well known that while forward scattering has no effect on the conductance of one-dimensional systems, backscattering off a static impurity suppresses the current. We study the effect of a time-dependent point impurity on the conductance of a one-channel quantum wire. At strong repulsive interaction (Luttinger liquid parameter g<1/2), backscattering renders the linear conductance greater than its value e^2/h in the absence of the impurity. A possible experimental realization of our model is a constricted quantum wire or a constricted Hall bar at fractional filling factors nu=1/(2n+1) with a time-dependent voltage at the constriction.