Abstract
The spin conductivity in the integrable spin- chain is known to be infinite at finite temperatures for anisotropies . Perturbations, which break integrability, e.g., a next-nearest neighbor coupling , render the conductivity finite. We construct numerically a nonlocal conserved operator which is responsible for the finite spin Drude weight of the integrable model and calculate its decay rate for small . This allows us to obtain a lower bound for the spin conductivity , where is finite for . We discuss the implication of our result for the general question how nonlocal conservation laws affect transport properties.
- Received 14 August 2007
DOI:https://doi.org/10.1103/PhysRevB.76.245108
©2007 American Physical Society