Superfluid Bosons and Flux Liquids: Disorder, Thermal Fluctuations, and Finite-Size Effects

摘要

The influence of different types of disorder (both uncorrelated andcorrelated) on the superfluid properties of a weakly interacting or dilute Bosegas, as well as on the corresponding quantities for flux line liquids inhigh-temperature superconductors at low magnetic fields are reviewed,investigated and compared. We exploit the formal analogy between superfluidbosons and the statistical mechanics of directed lines, and explore theinfluence of the different "imaginary time" boundary conditions appropriate fora flux line liquid. For superfluids, we discuss the density and momentumcorrelations, the condensate fraction, and the normal-fluid density as functionof temperature for two- and three-dimensional systems subject to a space- andtime-dependent random potential as well as conventional point-, line-, andplane-like defects. In the case of vortex liquids subject to point disorder,twin boundaries, screw dislocations, and various configurations of columnardamage tracks, we calculate the corresponding quantities, namely density andtilt correlations, the ``boson'' order parameter, and the tilt modulus. Thefinite-size corrections due to periodic vs. open "imaginary time" boundaryconditions differ in interesting and important ways. Experimental implicationsfor vortex lines are described briefly.