NMR Response in quasi one-dimensional Spin-1/2 Antiferromagnets

TL;DR

This paper analytically investigates NMR responses in quasi one-dimensional Spin-1/2 antiferromagnets, explaining experimental line shapes through interchain coupling effects using bosonization and numerical methods.

Contribution

It provides a parameter-free analytical formula for local susceptibility in finite spin chains, clarifying NMR line shapes influenced by interchain interactions.

Findings

Interchain coupling explains complex NMR lineshapes.

Bosonization accurately predicts local susceptibility.

Results agree with quantum Monte Carlo and DMRG simulations.

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 YBa$_2$Cu$_3$O$_{6.5}$ and on the spin-chain compound Sr$_2$CuO$_3$. Here we analytically calculate NMR spectra, compare with the available experimental data for Sr$_2$CuO$_3$, 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.