Field Theory for a Deuteron Quantum Liquid

TL;DR

This paper develops an effective field theory for a neutral, spin-1 deuteron condensate in certain astrophysical and experimental conditions, revealing unique collective excitations and symmetry-breaking phenomena.

Contribution

It introduces a novel effective Lagrangian for deuteron condensates, analyzing their excitations and symmetry properties in non-Lorentz-invariant systems.

Findings

Identifies a spin-zero condensate with aligned and anti-aligned spins.

Discovers two linear spin wave modes similar to antiferromagnets.

Finds gapped modes related to the Meissner effect.

Abstract

Based on general symmetry principles we study an effective Lagrangian for a neutral system of condensed spin-1 deuteron nuclei and electrons, at greater-than-atomic but less-than-nuclear densities. We expect such matter to be present in thin layers within certain low-mass brown dwarfs. It may also be produced in future shock-wave-compression experiments as an effective fuel for laser induced nuclear fusion. We find a background solution of the effective theory describing a net spin zero condensate of deuterons with their spins aligned and anti-aligned in a certain spontaneously emerged preferred direction. The spectrum of low energy collective excitations contains two spin waves with linear dispersions -- like in antiferromagnets -- as well as gapped longitudinal and transverse modes related to the Meissner effect -- like in superconductors. We show that counting of the Nambu-Goldstone modes of spontaneously broken internal and space-time symmetries obeys, in a nontrivial way, the rules of the Goldstone theorem for Lorentz non-invariant systems. We discuss thermodynamic properties of the condensate, and its potential manifestation in the low-mass brown dwarfs.