Perfect diode in quantum spin chains

TL;DR

This paper demonstrates a quantum spin chain setup that acts as a perfect diode for spin current, achieving high rectification by exploiting spectral matching between gapless and gapped segments.

Contribution

It introduces a novel quantum spin chain configuration that achieves perfect diode behavior through spectral matching, even with short chains.

Findings

Achieves rectification of order 10^4 with N=8 spins.

Demonstrates transition from diffusive to insulating behavior depending on current direction.

Provides spectral explanation for diode effect based on magnon excitations.

Abstract

We study the rectification of spin current in $XXZ$ chains segmented in two parts, each with a different anisotropy parameter. Using exact diagonalization and a matrix product states algorithm we find that a large rectification (of the order of $10^4$) is attainable even using a short chain of $N=8$ spins, when one half of the chain is gapless while the other has large enough anisotropy. We present evidence of diffusive transport when the current is driven in one direction and of a transition to an insulating behavior of the system when driven in the opposite direction, leading to a perfect diode in the thermodynamic limit. The above results are explained in terms of matching of spectrum of magnon excitations between the two halves of the chain.