Dynamics of two-dimensional dipole systems

Abstract

Using a combined analytical/molecular dynamics (MD) approach, we study the current fluctuation spectra and longitudinal and transverse collective mode dispersions of the classical two-dimensional (point) dipole system (2DDS) characterized by the ${\varphi }_D(r)={\mu }^2/r^3$ repulsive interaction potential; $\mu$ is the electric dipole strength. The interest in such two-dimensional dipole systems (2DDS) is twofold. First, the quasi-long range $1/r^3$ interaction makes the system a unique classical many body system, with a remarkable collective mode behavior. Second, the system may be a good model for a closely spaced semiconductor electron-hole bilayer, a system that is in the forefront of current experimental interest. The longitudinal collective excitations, which are of primary interest for the liquid phase, are acoustic at long wavelengths. At higher wave numbers and for sufficiently high coupling strength, we observe the formation of a deep minimum in the dispersion curve preceded by a sharp maximum; this is identical to what has been observed in the dispersion of the zero temperature bosonic dipole system, which in turn emulates so called roton-maxon excitation spectrum of the superfluid ${}^4$He. The analysis we present gives an insight into the emergence of this apparently universal structure, governed by strong correlations. We study both the liquid and the crystalline solid state. We also observe the excitation of combination frequencies, resembling the roton-roton, roton-maxon, etc. structures in ${}^4$He.

13 pages, 13 figures. Submitted to PRE

References in corpus (9)

• Strongly correlated 2D quantum phases with cold polar molecules: controlling the shape of the interaction potential
• Quantum phase transition in a two-dimensional system of dipoles
• Dynamical correlations and collective excitations of Yukawa liquids
• Wigner supersolid of excitons in electron-hole bilayers
• Effects of strong correlations for 2D Bose-Einstein condensed dipolar excitons
• Correlational Origin of the Roton Minimum
• Crystallization in mass-asymmetric electron-hole bilayers
• Acoustic dispersion in a two-dimensional dipole system
• Collective excitations in electron-hole bilayers

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• Unified description of sound velocities in strongly coupled Yukawa systems of different spatial dimensionality
• Note: Sound velocity of a soft sphere model near the fluid-solid phase transition
• Strong Coupling Effects in Binary Yukawa Systems
• Anisotropic superfluidity of two-dimensional excitons in a periodic potential
• Electronic rotons and Wigner crystallites in a two-dimensional dipole liquid
• Shear Viscosity in Two-Dimensional Dipole Systems
• Strongly coupled Yukawa trilayer liquid: Structure and dynamics
• Wave spectroscopy in a driven granular material
• Vibrational model of entropy in dense two-dimensional fluids
• Geometric Manifold Statistics of Turbulence-Impacted Beam Propagation and Compensation in Optical Communication
• Dynamical phase transitions in two-dimensional Brownian Matter