Phase diagram of dilute nuclear matter: Unconventional pairing and the BCS-BEC crossover

TL;DR

This paper maps the complex phase diagram of dilute nuclear matter, revealing multiple superfluid phases, unconventional pairing mechanisms, and phase transitions, including BCS-BEC crossover and tricritical points, under varying temperature and density conditions.

Contribution

It provides the first comprehensive phase diagram of dilute nuclear matter with unconventional pairing and detailed analysis of phase transitions and critical points.

Findings

Identification of three superfluid phases: LOFF, BCS, and phase-separated BCS.

Discovery of two tricritical points, including a Lifshitz point, in the phase diagram.

Observation of BCS-BEC crossover phenomena in dilute nuclear matter.

Abstract

We report on a comprehensive study of the phase structure of cold, dilute nuclear matter featuring a SD condensate at non-zero isospin asymmetry, within wide ranges of temperatures and densities. We find a rich phase diagram comprising three superfluid phases, namely a Larkin-Ovchinnikov-Fulde-Ferrell phase, the ordinary BCS phase, and a heterogeneous, phase-separated BCS phase, with associated crossovers from the latter two phases to a homogeneous or phase-separated Bose-Einstein condensate of deuterons. The phase diagram contains two tricritical points (one a Lifshitz point), which may degenerate into a single tetracritical point for some degree of isospin asymmetry.