Phase diagram of unconventional superconductor UPt3 in weak crystal field model

Abstract

We study the phase diagram of heavy fermion superconductor UPt3 within a phenomenological model with two nearly degenerate order parameters corresponding to theA1 andE1 irreducible representations. A weak effect on superconductivity from the crystal lattice is assumed. This assumption explains a closeness of two critical temperatures and yields parameters of the Ginzburg-Landau functional which lead to a single superconducting transition at pressures above critical: TheH-T diagram with a tetracritical point is recovered in theAE model. Experimental consequences which can distinguish this model from others are also discussed.