Nonreciprocal Quantum Transport at Junctions of Structured Leads

TL;DR

This paper introduces a mechanism for spin current rectification at junctions of structured leads, highlighting the role of asymmetry and spectral gaps, with potential applications in cold atom and quantum dot systems.

Contribution

It presents a new quantum model for spin rectification requiring minimal interacting elements and demonstrates agreement between analytical and numerical methods.

Findings

Transport depends on spatial asymmetry and spectral gaps in interacting leads.

A minimal model with two interacting two-level systems suffices for rectification.

Results are consistent with matrix-product-state calculations and observable in cold atom or quantum dot setups.

Abstract

We propose and analyze a mechanism for rectification of spin transport through a small junction between two spin baths or leads. For interacting baths we show that transport is conditioned on the spacial asymmetry of the quantum junction mediating the transport, and attribute this behavior to a gapped spectral structure of the lead-system-lead configuration. For non-interacting leads a minimal quantum model that allows for spin rectification requires an interface of only two interacting two-level systems. We obtain approximate results with a weak-coupling Born-master-equation in excellent agreement with matrix-product-state calculations that are extrapolated in time by mimicking absorbing boundary conditions. These results should be observable in controlled spin systems realized with cold atoms, trapped ions, or in electrons in quantum dot arrays.