Correlational Origin of the Roton Minimum

TL;DR

This paper provides evidence that the roton minimum in Bose-condensed systems originates from strong particle correlations, demonstrated through classical molecular dynamics simulations of 2D bosonic dipole systems.

Contribution

It shows that classical MD simulations can accurately reproduce the dispersion relation and roton features of low-temperature quantum Bose systems, highlighting the correlation-driven origin of the roton.

Findings

Roton minimum appears at high coupling strength.

Classical MD spectra show roton-roton and roton-maxon features.

Strong correlations are key to roton formation.

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 a 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.