Signatures of infinite randomness in transport properties of disordered spin chains

Abstract

We study the spin transport properties of some disordered spin chains with a special focus on the distribution of the frequency-dependent spin conductivity. In the cases of interest here, the systems are governed by an effectively infinite disorder at low energies. A hallmark of this behavior is the wide discrepancy between the average and the typical values of some physical quantities, which are described by extremely broad distributions. We show that such is also the case of the spin conductivity, whose average value is metallic but whose typical one, the physically relevant quantity, is insulating. This solves the apparent contradiction between the prediction of a spin metallic phase of the spin-1/2 disordered XX chain and its known localized behavior (after a mapping to free fermions). Our results are based on analytical and numerical implementations of a strong-disorder renormalization group as well as exact diagonalization studies. We present our analyses in very general terms, valid for systems of any spin $S$ value, but the cases of $S=1/2$ and 1 are studied in greater detail.

22 pages including Appendices, 9 figures

References in corpus (8)

• Rare region effects at classical, quantum, and non-equilibrium phase transitions
• Effects of dissipation on a quantum critical point with disorder
• Correlation amplitude and entanglement entropy in random spin chains
• Infinite randomness fixed point of the superconductor-metal quantum phase transition
• Dynamical conductivity at the dirty superconductor-metal quantum phase transition
• Strong-disorder renormalization-group study of the one-dimensional tight-binding model
• Random Antiferromagnetic SU(N) Spin Chains
• The correlation functions of certain random antiferromagnetic spin-1/2 critical chains