Jae Gil Kim

Thermodynamic properties of trapped, two-dimensional interacting Bose gases in Hartree-Fock approximation

We demonstrate the importance of the consistent treatment of mutual interaction between the condensate and the thermal component by applying the semiclassical Hartree-Fock model to the 2D trapped interacting Bose system. In contrast to the case where the interaction from the thermal component is neglected, the present system shows a lowering of the critical temperature and increase of the critical chemical potential due to the short-range repulsive interaction.

A general scheme for studying the stochastic dynamics of a parametric oscillator driven by coloured noise

The stochastic dynamics of a classical parametric oscillator driven by coloured noise with exponential correlation is studied both by analytical and numerical methods. The critical strength of the parametric modulation at which the motion of the oscillator becomes unbounded, and the dependence of this critical strength on the magnitude and the correlation length of the noise, are investigated. The results show that the critical strength does not depend on either the strength or the correlation length of the coloured noise, but that the squeezing induced by the parametric oscillation is enhanced by increasing the correlation length of the noise.

Hartree-Fock calculation for trapped, two-dimensional interacting Bose gases of finite size

The mean-field properties of trapped, two-dimensional interacting Bose gases of finite size are surveyed numerically. The coupled nonlinear equations of the Gross-Pitaevskii (GP) equation and the Hartree-Fock equation for the condensate and the thermal component, respectively, are calculated by the hybrid method, in which the GP equation and the low-lying excitations less than cut-off energy are calculated quantum mechanically using the basis representation, while the high-lying states are obtained within the local density approximation. Consistent solutions are obtained for the whole range of temperatures including the critical temperature by determining the thermodynamic chemical potential µ from the condition that the total atomic number must be the desired value, instead of identifying µ with the eigenvalue of the GP equation. Comparisons with the results of the semiclassical two-fluid model are presented.

Free electron dynamic response function: effects of temperature

Abstract We derive the analytical form of a temperature-dependent free electron dynamic response function starting from its Greens function representation by evaluating contributions from the poles of Greens function. The numerical analysis confirms that our analytical results are sufficiently accurate up to several times the Fermi temperature irrespective of ω dependence.