Non-trivial effect of dephasing: Enhancement of rectification of spin current in graded XX chains

TL;DR

This paper investigates how dephasing noise can enhance spin current rectification in graded XX spin chains, revealing complex behaviors and control mechanisms in non-equilibrium quantum systems.

Contribution

It demonstrates that dephasing can non-trivially enhance rectification and control spin current direction in graded XX chains, a novel insight into quantum transport.

Findings

Dephasing enhances rectification in homogeneous magnetic fields with graded interactions.

Fully graded systems can control spin current direction despite inverted baths.

Rectification phenomena may be common in quantum spin systems.

Abstract

In order to reveal mechanisms to control and manipulate spin currents, we perform a detailed investigation of the dephasing effects in the open XX model with a Lindblad dynamics involving global dissipators and thermal baths. Specifically, we consider dephasing noise modelled by current preserving Lindblad dissipators acting on graded versions of these spin systems, that is, systems in which the magnetic field and/or the spin interaction are growing (decreasing) along the chain. In our analysis, we study the non-equilibrium steady-state via the covariance matrix using the Jordan-Wigner approach to compute the spin currents. We find that the interplay between dephasing and graded systems gives rise to a non trivial behavior: when we have homogeneous magnetic field and graded interactions we have rectification enhancement mechanims, and when we have fully graded system we can control the spin current in order to keep the direction of the particle/spin flow even with inverted baths. We describe our result in detailed numerical analisys and we see that rectification in this simple model indicates that the phenomenon may be of general occurrence in quantum spin systems.