Non-linear Transport by Bethe Bound States

TL;DR

This paper derives an analytical expression for the non-linear Drude weight in the XXZ spin chain at infinite temperature, revealing dependence on anisotropy and quasiparticle string length, thus advancing understanding of non-linear spin transport.

Contribution

It provides the first analytical result for the non-linear Drude weight in the XXZ chain, highlighting the role of quasiparticle string length in transport properties.

Findings

Non-linear Drude weight depends on anisotropy and string length.

Analytical expression derived at infinite temperature.

Insights into quasiparticle transport mechanisms.

Abstract

We consider non-linear ballistic spin transport in the XXZ spin chain and derive an analytical result for the non-linear Drude weight $D^{(3)}$ at infinite temperatures. In contrast to the linear Drude weight $D^{(1)}$, we find that the result not only depends on anisotropy but also on the string length of the quasiparticles transporting the spin current. Our result provides further insights into transport by quasiparticles and raises questions about Luttinger liquid universality.