NMR multiple quantum coherences in quasi-one-dimensional spin systems: Comparison with ideal spin-chain dynamics

TL;DR

This study investigates the validity of modeling fluorapatite's 19F nuclear spins as a one-dimensional quantum system using NMR, analyzing how long-range and environmental couplings affect quantum coherence dynamics.

Contribution

The paper combines experimental, numerical, and analytical approaches to assess the accuracy of simplified 1D spin models in real fluorapatite systems.

Findings

Long-range and cross-chain couplings damp quantum coherence oscillations.

The simplified 1D model is valid within certain time scales.

Environmental interactions influence coherence decay.

Abstract

The 19F spins in a crystal of fluorapatite have often been used to experimentally approximate a one-dimensional spin system. Under suitable multi-pulse control, the nuclear spin dynamics may be modeled to first approximation by a double-quantum one-dimensional Hamiltonian, which is analytically solvable for nearest-neighbor couplings. Here, we use solid-state nuclear magnetic resonance techniques to investigate the multiple quantum coherence dynamics of fluorapatite, with an emphasis on understanding the region of validity for such a simplified picture. Using experimental, numerical, and analytical methods, we explore the effects of long-range intra-chain couplings, cross-chain couplings, as well as couplings to a spin environment, all of which tend to damp the oscillations of the multiple quantum coherence signal at sufficiently long times. Our analysis characterizes the extent to which fluorapatite can faithfully simulate a one-dimensional quantum wire.