NMR response in quasi–one-dimensional spin- antiferromagnets

¹  Max-Planck-Institut für Festkörperforschung - Heisenbergstrasse 1, D-70569 Stuttgart, Germany, EU
²  Technische Universität Kaiserslautern, Fachbereich Physik - Erwin-Schrödinger-Str., D-67663 Germany, EU
³  Laboratoire de Physique des Solides, Université Paris-Sud - UMR-8502 CNRS - 91405 Orsay, France, EU

Corresponding author: j.sirker@fkf.mpg.de

Received: 1 April 2009
Accepted: 24 May 2009

Abstract

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 YBa₂Cu₃O_6.5 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.