I discuss recent results obtained in collaboration with J. Schmalian, on the pairing of incoherent fermions near a quantum-critical point (QCP) in three dimensions. At weak coupling (interaction is smaller than fermionic bandwidth), the problem is only marginally different from BCS theory, and superconductivity is robust against phase fluctuations. I argue the pairing problem can be extended to the limit where the interaction is larger than the fermionic bandwidth. At strong coupling, we obtain the instability towards pair formation at a temperature of order of Fermi energy. However the superfluid stiffness is much smaller, and actual Tc is substantially reduced due to phase fluctuations. The results may be of relevance for superconductivity due to color magnetic interactions in quark matter and for systems close to a ferromagnetic quantum critical point with Ising symmetry.

University of Wisconsin