Towards the phase diagram of dense two-color matter

Abstract

We study two-color QCD with two flavors of Wilson fermion as a function of quark chemical potential $\ensuremath{\mu}$ and temperature $T$. We find evidence of a superfluid phase at intermediate $\ensuremath{\mu}$ and low $T$ where the quark number density and diquark condensate are both very well described by a Fermi sphere of nearly free quarks disrupted by a BCS condensate. Our results suggest that the quark contribution to the energy density is negative (and balanced by a positive gauge contribution), although this result is highly sensitive to details of the energy renormalization. We also find evidence that the chiral condensate in this region vanishes in the massless limit. This region gives way to a region of deconfined quark matter at higher $T$ and $\ensuremath{\mu}$, with the deconfinement temperature, determined from the renormalized Polyakov loop, decreasing only very slowly with increasing chemical potential. The quark number susceptibility ${\ensuremath{\chi}}_{q}$ does not exhibit any qualitative change at the deconfinement transition. We argue that this is because ${\ensuremath{\chi}}_{q}$ is not an appropriate measure of deconfinement for two-color QCD at high density.