Dynamics in the S=1/2 one-dimensional antiferromagnet Sr₂CuO₃ via 63Cu NMR

The 63 Cu 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/T2G∝ 1/T, consistent with scaling theory. The value of T1 √T/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. © 1996 The American Physical Society.