Group Seminar via Zoom: Anomalous transport in integrable spin chains

Sarang Gopalakrishnan, College of Staten Island (CSI) CUNY
Group meeting via video conference (Zoom)
Tuesday, April 20, 2021, 4:00pm (MEZ)

Dealing with the unique situation of partial lock downs worldwide and home office solutions at our Institute due to the current spreading of the Covid 19 virus, we are now holding our group seminars and journal clubs via video conference.
This procedure enables us to continue our research, enhance discussions and exchange important information.

Abstract:

The XXZ spin chain is a canonical model of one-dimensional quantum magnetism. We consider spin transport at nonzero temperature in this model. Spin transport is ballistic in the easy-plane regime, diffusive in the easy-axis regime, and superdiffusive at the isotropic Heisenberg point. Energy transport, by contrast, is ballistic in all cases. The framework of generalized hydrodynamics offers an elementary explanation of these phenomena in terms of the quasiparticle content of the XXZ model. It also predicts new transport anomalies, e.g., in local relaxation in the easy-axis regime in the presence of a magnetic field, and in the a.c. conductivity in the easy-plane regime. These anomalies come from the asymptotic behavior of large semiclassical bound states of many quasiparticles. Superdiffusion is generic for integrable models with nonabelian symmetries, and stems from the presence of stable solitons made up of Goldstone modes. As we argue, these solitons remain long-lived even away from precisely integrable limits.

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