Theory of Nuclear Magnetic Relaxation in Haldane Gap Materials: An Illustration of the Use of (1+1)-Dimensional Field Theory Techniques

TL;DR

This paper develops a comprehensive theoretical framework for nuclear magnetic relaxation in Haldane Gap materials, employing (1+1)-dimensional field theory techniques and considering various physical effects, with comparisons to experimental data.

Contribution

It introduces a new impurity theory for broken chain ends and applies advanced field theory methods to analyze relaxation phenomena in Haldane Gap systems.

Findings

The theory matches experimental relaxation rates in NENP.

Impurity effects significantly influence relaxation behavior.

Interchain couplings and hyperfine interactions are quantitatively analyzed.

Abstract

A comprehensive theory of nuclear magnetic relaxation is developed for Haldane Gap materials using nonlinear sigma, boson and fermion models. We include a thorough discussion of of the effects of interchain couplings, nearest neighbour hyperfine couplings and crystal structure. We also introduce a new theory of impurities corresponding to broken chain ends weakly coupled to bulk magnons. The work is compared to recent experiments on NENP.