Finite-temperature Drude weight within the anisotropic Heisenberg chain

TL;DR

This paper investigates the finite-temperature Drude weight in the anisotropic Heisenberg chain using exact diagonalization, revealing how system size and anisotropy influence spin transport properties.

Contribution

It provides a detailed analysis of finite-size effects and low-frequency anomalies in calculating the Drude weight, especially highlighting differences between even and odd chain lengths.

Findings

D(T) approaches zero near the isotropic point at high T

For Δ>2, D is nearly conserved and overlaps with the energy current

Odd chains yield more reliable scaling results

Abstract

Finite-temperature Drude weight (spin stiffness) D(T) is evaluated within the anisotropic spin-1/2 Heisenberg model on a chain using the exact diagonalization for small systems. It is shown that odd-side chains allow for more reliable scaling and results, in particular, if one takes into account corrections due to low-frequency finite-size anomalies. At high T and zero magnetization D is shown to scale to zero approaching the isotropic point {\Delta}=1. On the other hand, for {\Delta}>2 at all magnetizations D is nearly exhausted with the overlap with the conserved energy current. Results for the T variation D(T) are also presented.