Unconventional Color Superconductor

Abstract

Superfluidity or superconductivity with mismatched Fermi momenta appears in many systems such as charge neutral dense quark matter, asymmetric nuclear matter, and in imbalanced cold atomic gases. The mismatch plays the role of breaking the Cooper pairing, and the pair-breaking state cannot be properly described in the framework of standard BCS theory. I give a brief review on recent theoretical development in understanding unconventional color superconductivity, including gapless color superconductor, the chromomagnetic instabilities and the Higgs instability in the gapless phase. I also introduce a possible new framework for describing unconventional color superconductor.