Simulating the interplay of dipolar and quadrupolar interactions in NMR by spin dynamic mean-field theory

TL;DR

This paper introduces an efficient spin dynamic mean-field theory (spinDMFT) for simulating NMR in systems with many spins, accurately capturing dipolar and quadrupolar interactions and aligning well with experimental data.

Contribution

The paper develops and applies spinDMFT to include quadrupolar interactions exactly, enabling non-perturbative simulations of complex spin systems in NMR.

Findings

SpinDMFT accurately reproduces experimental NMR data for aluminium nitride.

The method effectively incorporates quadrupolar terms without perturbation.

Quantum effects are shown to be significant in the studied systems.

Abstract

The simulation of nuclear magnetic resonance (NMR) experiments is a notoriously difficult task, if many spins participate in the dynamics. The recently established dynamic mean-field theory for high-temperature spin systems (spinDMFT) represents an efficient yet accurate method to deal with this scenario. SpinDMFT reduces a complex lattice system to a time-dependent single-site problem, which can be solved numerically with small computational effort. Since the approach retains local quantum degrees of freedom, a quadrupolar term can be exactly incorporated. This allows us to study the interplay of dipolar and quadrupolar interactions for any parameter range, i.e., without the need for a perturbative treatment. We obtain a remarkable agreement with experimental data for an aluminium nitride monocrystal, which strongly suggests the use of spinDMFT as a prediction tool. Furthermore, we draw a comparison between a quantum-mechanical and a classical version of spinDMFT showing that local quantum effects are of great importance for the studied type of system.