Physics – Condensed Matter – Other Condensed Matter
Scientific paper
2008-04-03
Physics
Condensed Matter
Other Condensed Matter
37 pages, submitted to Phys. Rev. B
Scientific paper
10.1103/PhysRevB.78.045304
We calculate the full density response function, and from it the long-wavelength acoustic dispersion for a two-dimensional system of strongly coupled point dipoles interacting through a 1/r^3 potential at arbitrary degeneracy. Such a system has no RPA limit and the calculation has to include correlations from the outset. We follow the Quasi-Localized Charge (QLC) approach, accompanied by Molecular Dynamics (MD) simulations. Similarly to what has been recently reported for the closely spaced classical electron-hole bilayer [G. J. Kalman et al. Phys. Rev. Lett. 98, 236801 (2007)] and in marked contrast to the RPA, we report a long-wavelength acoustic phase velocity that is wholly maintained by particle correlations and varies linearly with the dipole moment p. The oscillation frequency, calculated both in an extended QLC approximation and in the Singwi-Tosi-Land-Sjolander approximation, is invariant in form over the entire classical to quantum domains all the way down to zero temperature. Based on our classical MD-generated pair distribution function data and on ground-state energy data generated by recent quantum Monte Carlo simulations on a bosonic dipole system [Astrakharchik et al, Phys. Rev. Lett. 98, 060405 (2007)], there is a good agreement between the QLCA kinetic sound speeds and the standard thermodynamic sound speeds in both the classical and quantum domains.
Donkó Zoltan
Golden Kenneth I.
Hartmann Peter
Kalman Gabor J.
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