Finding the elusive sliding phase in superfluid-normal phase transition smeared by c-axis disorder

摘要

We consider a system composed of a stack of weakly Josephson coupledsuperfluid layers with c-axis disorder in the form of random superfluidstiffnesses and vortex fugacities in each layer as well as random inter-layercoupling strengths. In the absence of disorder this system has a 3D XY typesuperfluid-normal phase transition as a function of temperature. We develop afunctional renormalization group to treat the effects of disorder, anddemonstrate that the disorder results in the smearing of the superfluid normalphase transition via the formation of a Griffiths phase. Remarkably, in theGriffiths phase, the emergent power-law distribution of the inter-layercouplings gives rise to sliding Griffiths superfluid, with an anisotropiccritical current, and with a finite stiffness in a-b direction along thelayers, and a vanishing stiffness perpendicular to it.