Energy current manipulation and reversal of rectification in graded XXZ spin chains

TL;DR

This paper investigates how energy and spin currents in graded XXZ spin chains can be manipulated and reversed using external magnetic fields, revealing complex rectification behaviors with potential experimental implications.

Contribution

It demonstrates control and reversal of energy and spin current rectification in graded XXZ chains through external magnetic fields and internal parameter tuning.

Findings

Energy current rectification and reversal due to magnetic fields.

Opposite rectification directions for energy and spin currents.

Current inversion with increasing system asymmetry.

Abstract

This work is devoted to the investigation of nontrivial transport properties in many-body quantum systems. Precisely, we study transport in the steady state of spin-1/2 Heisenberg XXZ chains, driven out of equilibrium by two magnetic baths with fixed, different magnetization. We take graded versions of the model, i.e., asymmetric chains in which some structure gradually changes in space. We investigate how we can manipulate and control the energy and spin currents of such chains by tuning external and/or inner parameters. In particular, we describe the occurrence of energy current rectification and its reversal due to the application of external magnetic fields. We show that, after carefully chosen the inner parameters of the system, by turning on an external magnetic field we can find spin and energy currents propagating in different directions. More interestingly, we may find cases in which rectifications of the energy and of the spin currents occur in opposite directions, i.e., if the energy current is larger when flowing from left to right side, then the spin current is larger if it flows from the right to left side. We still describe situations with inversion of the energy current direction as we increase the system asymmetry. We stress that our work aims the development of theoretical knowledge as well as the stimulation of future experimental applications.