Conductance beyond the Landauer limit and charge pumping in quantum wires

TL;DR

This paper demonstrates that a periodically driven quantum wire can exhibit conductance beyond the Landauer limit and can pump charge using microwave radiation, revealing new Floquet physics in quantum transport.

Contribution

It introduces a method to measure Floquet states via conductance in a quantum point contact and shows conductance exceeding the Landauer limit with microwave irradiation.

Findings

Conductance surpasses one quantum unit in a driven quantum wire.

The system can generate a strong photo-current with linearly polarized light.

Floquet states can be directly probed through conductance measurements.

Abstract

Periodically driven systems, which can be described by Floquet theory, have been proposed to show characteristic behavior that is distinct from static Hamiltonians. Floquet theory proposes to describe such periodically driven systems in terms of states that are indexed by a photon number in addition to the usual Hilbert space of the system. We propose a way to measure directly this additional Floquet degree of freedom by the measurement of the DC conductance of a single channel quantum point contact. Specifically, we show that a single channel wire augmented with a grating structure when irradiated with microwave radiation can show a DC conductance above the limit of one conductance quantum set by the Landauer formula. Another interesting feature of the proposed system is that being non-adiabatic in character, it can be used to pump a strong gate-voltage dependent photo-current even with linearly polarized radiation.