Issue |
EPL
Volume 85, Number 2, January 2009
|
|
---|---|---|
Article Number | 20009 | |
Number of page(s) | 6 | |
Section | General | |
DOI | https://doi.org/10.1209/0295-5075/85/20009 | |
Published online | 04 February 2009 |
RPA approach to supersolidity
Max-Planck-Institute for the Physics of Complex Systems - D-01187 Dresden, Germany, EU and Nonlinear Physics Centre, Australian National University - Canberra, ACT 0200, Australia
Corresponding author: gulacsi@pks.mpg.de
Received:
9
October
2008
Accepted:
5
January
2009
We investigate the newly discovered supersolid phase by solving in
random phase approximation the anisotropic Heisenberg model of the hard-core boson
lattice.
We include nearest- and next-nearest-neighbor interactions and calculate exactly all pair
correlation functions in a cumulant expansion scheme. Here we clarify the controversy over
the role of the vacancies and defects, which have long been proposed to have a crucial
role in the formation of a SS phase. We show that vacancies and interstitials will be
present even at zero temperature in the supersolid phase. This phase is characterized by
Bose condensation of the vacancies as well as the interstitials and may be regarded as
a bond-ordered wave as it exhibits alternating strength of the expectation value of the
kinetic energy term on bonds. We also show that the superfluid-to-supersolid transition is
triggered by a collapsing roton minimum, however, the supersolid phase is stable against
spontaneously induced superflow.
PACS: 05.30.Jp – Boson systems / 67.80.-s – Quantum solids / 67.80.bd – Superfluidity in solid 4He, supersolid 4He
© EPLA, 2009
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