DescriptionWhen bulk helium-4 is cooled below T = 2.18 K, it undergoes a thermodynamic phase transition to a superfluid, characterized by zero viscosity and quantization of flow. The superfluid state of matter is a macroscopic manifestation of quantum mechanics, as it can be described by a single complex wave function with a phase that does not depend on position. The phase coherence can be probed in a container filled with helium-4, by reducing one or more of its dimensions until they are smaller than the coherence length; the spatial distance over which order propagates. As this dimensional reduction occurs, enhanced thermal and quantum fluctuations push the transition to the superfluid state to lower temperatures. However, this trend can be countered via the proximity effect, where a bulk 3D superfluid is coupled to a low (2D) dimensional superfluid via a weak link producing superfluid correlations in the film at temperatures above the Kosterlitz-Thouless temperature. Recent experiments probing the coupling between 3D and 2D superfluid helium-4 have uncovered an anomalously large proximity effect, leading to an enhanced superfluid density that cannot be explained using the correlation length alone.We intend to explore the microscopic origin of this enhanced proximity effect via large scale quantum Monte Carlo simulations of helium-4 in a topologically non-trivial geometry that incorporates the important aspects of the experiments. We will modify, test and deploy our research group's home-built high performance worm algorithm path integral quantum Monte Carlo code ( at low temperatures with an eye toward improving efficiency through enhanced parallelization and hybridization.
OrganizationUniversity of Vermont
Sponsor Campus GridOSG-XSEDE
Principal Investigator
Adrian Del Maestro
Field Of ScienceMaterials Science