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POSSIBLE SUPERFLUID PHASE OF PARAHYDROGEN ON NANOPATTERNED SURFACES

  • Author / Creator
    Idowu, Saheed A
  • We study by computer simulations the low temperature properties of small parahydrogen clusters (free clusters) and the effect of confinement on the energetics and superfluid properties in two-dimensions (2D). Computed energetics for the free clusters are in quantitative agreement with that reported in the only previous study [M. C. Gordillo and D. M. Ceperley, Phys. Rev. B 65, 174527 (2002)], but a generally strong superfluid response is obtained for clusters with more than ten molecules. All the free clusters, including the smallest one, feature a well-defined, clearly identifiable solidlike structure; with only one possible exception, those with fewer than N = 25 molecules are (almost) entirely superfluid at the lowest temperature considered (i.e., T = 0.25 K), and are thus referred to as nanoscale “supersolids”. The superfluid response in the low temperature limit of the confined clusters is found to remain commensurable in magnitude to that of the free clusters, for clusters fewer than twenty molecules, within a wide range of depth and size of the confining well. The flexibility of the superfluid response is traceable to the “supersolid” character of these clusters. We explore the possibility of establishing a bulk 2D superfluid “cluster crystal” phase of p-H2, in which a global superfluid response would arise from tunnelling of molecules across adjacent unit cells. Computed energetics suggests that for a cluster of about ten molecules, such a phase may be thermodynamically stable against the formation of the equilibrium insulating crystal, for values of cluster crystal lattice constant possibly allowing tunnelling across adjacent unit cells.

  • Subjects / Keywords
  • Graduation date
    2015-11
  • Type of Item
    Thesis
  • Degree
    Master of Science
  • DOI
    https://doi.org/10.7939/R3SQ8QR8P
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
  • Language
    English
  • Institution
    University of Alberta
  • Degree level
    Master's
  • Department
    • Department of Physics
  • Supervisor / co-supervisor and their department(s)
    • Boninsegni, Massimo (Physics)
  • Examining committee members and their departments
    • Jung, Jang (Physics)
    • Chow, Kim (Physics)
    • Currie, Claire (Geophysics)