Finding the Elusive Sliding Phase in the Superfluid-Normal Phase Transition Smeared by \(c\)-Axis Disorder

Abstract

We consider a stack of weakly Josephson coupled superfluid layers with (c)-axis disorder in the form of random superfluid stiffnesses and vortex fugacities in each layer as well as random interlayer coupling strengths. In the absence of disorder this system has a 3D (XY) type superfluid-normal phase transition as a function of temperature. We develop a functional renormalization group to treat the effects of disorder, and demonstrate that the disorder results in the smearing of the superfluid-normal phase transition via the formation of a Griffiths phase. Remarkably, in the Griffiths phase, the emergent power-law distribution of the interlayer couplings gives rise to a sliding Griffiths superfluid, with a finite stiffness in the (a-b) direction along the layers, and a vanishing stiffness perpendicular to it.