Dynamics in theS=1/2One-Dimensional AntiferromagnetSr2CuO3via63CuNMR

Abstract
The 63Cu nuclear spin-lattice relaxation rate ( 1/T1) and the Gaussian spin-echo decay rate ( 1/T2G) have been measured in the spin 1/2 one-dimensional antiferromagnet Sr2CuO3 ( J=2200K) in the temperature range from 20 to 280 K. We observed the following temperature dependencies: 1/T1=const and 1/T2G1/T, consistent with scaling theory. The value of T1T/T2G is also in good agreement with theoretical prediction. These results provide strong experimental support for the quantum critical behavior of the S=1/2 1D Heisenberg model at finite temperatures.