Phase diagram of chiral quark matter: From weakly to strongly coupled Fulde-Ferrell phase

Journal Article · Thu Oct 01 04:00:00 EDT 2009 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.80.074022· OSTI ID:21325237

Sedrakian, Armen ^[1]; Rischke, Dirk H ^[1]

---

1. Institute for Theoretical Physics, J. W. Goethe University, D-60438 Frankfurt am Main (Germany)

We calculate the phase diagram of two-flavor quark matter within the Nambu-Jona-Lasinio (NJL) model in the temperature-flavor asymmetry plane in the case where there are three competing phases: the homogeneous Bardeen-Cooper-Schrieffer (BCS) phase, the unpaired phase, and a phase with broken spatial symmetry, which is here taken to be the counterpart of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase in condensed matter physics. The system belongs to the universality class of paramagnetic-ferromagnetic-helical systems, and therefore contains a tricritical Lifshitz point in its phase diagram, where the momentum scale characterizing the breaking of translational invariance has a critical exponent of 1/2 to leading order. Upon varying the coupling constant of the theory we find that in weak coupling, the FFLO phase is favored at arbitrary flavor asymmetries for sufficiently low temperatures; at intermediate coupling its occupancy domain is shifted towards larger asymmetries. Strong coupling features a new regime of an inhomogeneous FF state, which we identify with a current-carrying Bose-Einstein condensate of tightly bound up and down quarks. The temperature and asymmetry dependence of the gap function is studied. It is shown that the anomalous temperature dependence of the gap in the homogeneous, flavor-asymmetric phase is transformed into a normal dependence (self-similar to the BCS phase) at arbitrary coupling, once the FF phase is allowed for. We analyze the occupation numbers and the Cooper-pair wave function and show that when the condensate momentum is orthogonal to the particle momentum the minority component contains a blocking region (breach) around the Fermi sphere in the weak-coupling limit, which engulfs more low-momentum modes as the coupling is increased, and eventually leads to a topological change in strong coupling, where the minority Fermi sphere contains either two occupied strips or an empty sphere. For nonorthogonal momenta, the blocking region is either reduced or extinct, i.e., no topological changes are observed.

• OSTI ID: 21325237
• Journal Information: Physical Review. D, Particles Fields, Journal Name: Physical Review. D, Particles Fields Journal Issue: 7 Vol. 80; ISSN PRVDAQ; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ASYMMETRY
BCS THEORY
BOSE-EINSTEIN CONDENSATION
CHIRALITY
COMPUTERIZED SIMULATION
CONDENSATES
COOPER PAIRS
COUPLING CONSTANTS
D QUARKS
FLAVOR MODEL
INTERMEDIATE COUPLING
OCCUPATIONS
PARAMAGNETISM
PHASE DIAGRAMS
QUARK MATTER
STRONG-COUPLING MODEL
SYMMETRY
SYMMETRY BREAKING
TEMPERATURE DEPENDENCE
WAVE FUNCTIONS