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Edge Logarithmic Corrections probed by Impurity NMR

V. Brunel, M. Bocquet, Th. Jolicoeur

cond-mat.str-elarXiv:cond-mat/9902028

Abstract

Semi-infinite quantum spin chains display spin autocorrelations near the boundary with power-law exponents that are given by boundary conformal field theories. We show that NMR measurements on spinless impurities that break a quantum spin chain lead to a spin-lattice relaxation rate 1/T1edge that has a temperature dependence which is a direct probe of the anomalous boundary exponents. For the antiferromagnetic S=1/2 spin chain, we show that 1/T1edge behaves as T (log T)2 instead of (log T)1/2 for a bulk measurement. We show that, in the case of a one-dimensional conductor described by a Luttinger liquid, a similar measurement leads to a relaxation rate 1/T1edge behaving as T, independent of the anomalous exponent Krho.

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