Spin transport in the S=1/2 Heisenberg antiferromagnetic chain KCuF3

Spin transport in quantum spin chains has recently attracted renewed attention following theoretical predictions of a novel transport regime at high temperatures: the spin-1/2 Heisenberg model is predicted to exhibit spin super-diffusion that is neither conventional diffusive nor ballistic transport. We aim to determine the transport mode in the spin-1/2 Heisenberg antiferromagnet KCuF3 by measuring muon spin relaxation rate as a function of the applied longitudinal field by extracting the exponent from the power-law behaviour.