Phase order in superfluid helium films

Abstract

Classic experimental data on helium films are transformed to estimate a finite-size phase order parameter that measures the thermal degradation of the condensate fraction in the two-dimensional superfluid. The order parameter is found to evolve thermally with the exponent $\beta =3{\pi }^2/128$, a characteristic, in analogous magnetic systems, of the Berezinskii-Kosterlitz-Thouless (BKT) phase transition. Universal scaling near the BKT fixed point generates a collapse of experimental data on helium and ferromagnetic films, and implies new experiments and theoretical protocols to explore the phase order. These results give a striking example of experimental finite-size scaling in a critical system that is broadly relevant to two-dimensional Bose fluids.

6 pages, 2 figures

References in corpus (3)

• Bose-Einstein Condensation in Magnetic Insulators
• Critical Casimir force in ${}^4$He films: confirmation of finite-size scaling
• The importance of XY anisotropy in Sr2IrO4 revealed by magnetic critical scattering experiments

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