Non-magnetic impurities break a quantum spin chain into finite segments and induce Friedel-like oscillations in the local susceptibility near the edges. The signature of these oscillations has been observed in Knight shift experiments on the high-temperature superconductor YBa2Cu3O6.5 and on the spin-chain compound Sr2CuO3. Here we analytically calculate NMR spectra, compare with the available experimental data for Sr2CuO3, and show that the interchain coupling is responsible for the complicated and so far unexplained lineshape. Our results are based on a parameter-free formula for the local susceptibility of a finite spin chain obtained by bosonization which is checked by comparing with quantum Monte Carlo and density-matrix renormalization group calculations.
@article{arxiv.0811.2106,
title = {NMR Response in quasi one-dimensional Spin-1/2 Antiferromagnets},
author = {J. Sirker and N. Laflorencie},
journal= {arXiv preprint arXiv:0811.2106},
year = {2009}
}