Correlational origin of the roton minimum

¹  Department of Physics, Boston College - Chestnut Hill, MA 02467, USA
²  Research Institute for Solid State Physics and Optics of the Hungarian Academy of Sciences H-1525 Budapest, POB 49. Hungary, EU
³  Department of Mathematics and Statistics, Department of Physics University of Vermont Burlington, VT 05401-1455, USA
⁴  Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel D-24098 Kiel, Germany, EU

Received: 25 February 2010
Accepted: 28 May 2010

Abstract

We present compelling evidence supporting the conjecture that the origin of the roton in Bose-condensed systems arises from strong correlations between the constituent particles. By studying the two-dimensional bosonic dipole systems paradigm, we find that classical molecular-dynamics (MD) simulations provide a faithful representation of the dispersion relation for a low-temperature quantum system. The MD simulations allow one to examine the effect of coupling strength on the formation of the roton minimum and to demonstrate that it is always generated at a sufficiently high enough coupling. Moreover, the classical images of the roton-roton, roton-maxon, etc. states also appear in the MD simulation spectra as a consequence of the strong coupling.