Correlated atomic motion, phonons and spin-ordering in bcc $^{3}$He

TL;DR

This paper introduces a new model explaining nuclear magnetism in solid bcc $^{3}$He through correlated zero-point motion, linking phonon spectra and magnetic ordering with a single parameter.

Contribution

It presents a unified model that accounts for phonon spectra and nuclear magnetic ordering in bcc $^{3}$He using correlated zero-point motion and electric dipoles.

Findings

Accurately describes the u2d2 symmetry of the ordered phase.

Reproduces the volume dependence of magnetic interactions.

Provides a single-parameter model for phonons and magnetism.

Abstract

We propose a new way to treat nuclear magnetism of solid $^{3}$He. We argue that the magnetic interaction arises indirectly as a consequence of correlated zero-point motion of the ions. This motion lowers the energy of the ground state, and results in a coherent state of oscillating electric dipoles. Distortion of the electronic wavefunctions leads to hyperfine magnetic interactions with the nuclear spin. Our model describes both the phonon spectra and the nuclear magnetic ordering of bcc $^{3}$He using a single parameter, the dipolar interaction energy $E_{0}$. The model yields correctly both the u2d2 symmetry of the ordered phase and the volume dependence of the magnetic interaction.