Universal conductance dips and fractional excitations in a two-subband quantum wire

TL;DR

This paper presents a theoretical study of conductance dips in a two-subband quantum wire with a helical magnetic field, revealing a universal signature of fractional excitations due to electron interactions.

Contribution

It uncovers a novel backscattering mechanism involving helical magnetic fields and Coulomb interactions, leading to universal conductance dips in quasi-one-dimensional systems.

Findings

Identification of a backscattering mechanism causing conductance dips

Universal conductance dips independent of material parameters

Signatures of fractional excitations in strongly correlated fermion systems

Abstract

We theoretically investigate a quasi-one-dimensional quantum wire, where the lowest two subbands are populated, in the presence of a helical magnetic field. We uncover a backscattering mechanism involving the helical magnetic field and Coulomb interaction between the electrons. The combination of these ingredients results in scattering resonances and partial gaps which give rise to non-standard plateaus and conductance dips at certain electron densities. The positions and values of these dips are independent of material parameters, serving as direct transport signatures of this mechanism. Our theory applies to generic quasi-one-dimensional systems, including a Kondo lattice and a quantum wire subject to intrinsic or extrinsic spin-orbit coupling. Observation of the universal conductance dips would identify a strongly correlated fermion system hosting fractional excitations, resembling the fractional quantum Hall states.