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.
Highlights
Quasi-one-dimensional conductors, such as semiconducting nanowires or quantum point contacts, are typical elements of nanocircuits
We demonstrate a mechanism for universal conductance dips and fractional excitations
The wires realize Kondo lattices, in which nuclear spins are ordered into a helical pattern at dilution fridge temperature [e.g., O(10 mK)–O(100 mK) for GaAs and InAs wires], as predicted theoretically in Refs. [52,53] and indicated in the experiment with cleaved edge overgrowth GaAs quantum wires in Ref. [13]
Summary
Quasi-one-dimensional conductors, such as semiconducting nanowires or quantum point contacts, are typical elements of nanocircuits. Observation of zero-bias conductance peaks in proximitized Rashba nanowires [28,29,30], which hint at the presence of Majorana bound states, has stimulated numerous sequential studies on topological aspects of the quasi-one-dimensional systems [31] It motivated alternative setups for the realization of Majorana bound states, in which the external magnetic field and spin-orbit coupling are replaced by other ingredients. Incorporating these ingredients has led to the discovery of different candidate platforms and more exotic topological phases characterized by, e.g., parafermions or fractionally charged fermions We merge these ingredients by considering an interacting two-subband quantum wire in the presence of a helical (spatially rotating) magnetic field, which induces a spin-selective partial gap in the lower subband. With the spacing Eg between the two subbands; see Fig. 1
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