Dynamics and Transport in Random Antiferromagnetic Spin Chains

TL;DR

This paper investigates the low-frequency dynamical and transport properties of random antiferromagnetic spin chains, revealing their 'spin-metal' behavior and transitions driven by disorder and anisotropy.

Contribution

It provides the first detailed analysis of the dynamic structure factor and transport in these disordered spin chains, highlighting their unique 'spin-metal' phase.

Findings

Random singlet phases exhibit divergent low-frequency conductivity.

Spin chains undergo 'metal-insulator' transitions controlled by disorder and anisotropy.

Dynamic structure factors are characterized for both spin-1/2 and spin-1 chains.

Abstract

We present the first results on the low-frequency dynamical and transport properties of random antiferromagnetic spin chains at low temperature ($T$). We obtain the momentum and frequency dependent dynamic structure factor in the Random Singlet (RS) phases of both spin-1/2 and spin-1 chains, as well as in the Random Dimer phase of spin-1/2 chains. We also show that the RS phases are unusual `spin-metals' with divergent low-frequency conductivity at T=0, and follow the spin conductivity through `metal-insulator' transitions tuned by the strength of dimerization or Ising anisotropy in the spin-1/2 case, and by the strength of disorder in the spin-1 case.