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Sliding phase in randomly stacked 2d superfluids/superconductors

by Nicolas Laflorencie - 4 October 2012

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In a recent letter published in Europhys. Lett. 99, 66001 (2012), Nicolas Laflorencie from LPT showed using large scale quantum Monte Carlo simulations on a lattice bosonic model of stacked superfluid/superconducting layers that a unconventional sliding superfluid phase is expected over a finite temperature window.

Using large-scale quantum Monte Carlo simulations of lattice bosonic models, we precisely investigate the effect of weak Josephson tunneling between 2D superfluid or superconducting layers. In the clean case, the Kosterlitz-Thouless transition immediately turns into 3DXY, with phase coherence and superflow in all spatial directions, and a strong enhancement of the critical temperature. However, when disorder is present, rare regions fluctuations can lead to an intermediate finite-temperature phase —the so-called sliding regime— where only 2D superflow occurs within the layers without any transverse superfluid coherence, while a true 3D Bose-Einstein condensate exists. Critical properties of such an unconventional regime are carefully investigated.