Healing of defects in random antiferromagnetic spin chains

¹ Department of Physics, University of Massachusetts - Amherst, MA 01003, USA
² Department of Physics, University of California - Berkeley, CA 94720, USA
³ Materials Sciences Division, Lawrence Berkeley National Laboratory - Berkeley, CA 94720, USA
⁴ Department of Physics and Astronomy, University of Southern California - Los Angeles, CA 90089-0484, USA
⁵ Institut de Physique Théorique, CEA Saclay - 91191 Gif-sur-Yvette, France

Received: 31 August 2017
Accepted: 25 October 2017

Abstract

We study the effects of a weakened link in random antiferromagnetic spin chains. We show that healing occurs, and that homogeneity is restored at low energy, in a way that is qualitatively similar to the fate of impurities in clean ferromagnetic spin chains, or in Luttinger liquids with attractive interactions. Healing in the random case occurs even without interactions, and is characteristic of the random singlet phase. Using real-space renormalization group and exact diagonalization methods, we characterize this universal healing crossover by studying the entanglement across the weak link. We identify a crossover healing length that separates a regime where the system is cut in half by the weak link from a fixed point where the spin chain is healed. Our results open the way to the study of impurity physics in disordered spin chains.