Static and dynamic correlation functions of a two-dimensional quantum electron fluid

Spin polarized and density modulated phases in symmetric electron-electron and electron-hole bilayers

We have studied symmetric electron-electron and electron-hole bilayers to explore the stable homogeneous spin phase and the feasibility of inhomogeneous charge-/spin-density ground states. The former is resolved by comparing the ground-state energies in states of different spin polarizations, while the latter is resolved by searching for a divergence in the wavevector-dependent static charge/spin susceptibility. For this endeavour, we have used the dielectric approach within the self-consistent mean-field theory of Singwi et al. We find that the inter-layer interactions tend to change an abrupt spin-polarization transition of an isolated layer into a nearly gradual one, even though the partially spin-polarized phases are not clearly stable within the accuracy of our calculation. The transition density is seen to decrease with a reduction in layer spacing, implying a suppression of spin polarization by inter-layer interactions. Indeed, the suppression shows up distinctly in the spin susceptibility computed from the spin-polarization dependence of the ground-state energy. However, below a critical layer spacing, the unpolarized liquid becomes unstable against a charge-density-wave (CDW) ground state at a density preceding full spin polarization, with the transition density for the CDW state increasing on further reduction in the layer spacing. Due to attractive e-h correlations, the CDW state is found to be more pronounced in the e-h bilayer. On the other hand, the static spin susceptibility diverges only in the long-wavelength limit, which simply represents a transition to the homogeneous spin-polarized phase.

Confinement and correlation effects on plasmons in an atom-scale metallic wire

We have studied the effect of confinement and correlations on the plasmon dispersion in an atom-scale metallic wire by determining the electron density response function. The wire electrons are modelled as comprising a quasi-one-dimensional homogeneous gas, with different transverse confinement models. The response function is calculated by including electron correlations beyond the random-phase approximation within the self-consistent mean-field approach of Singwi et al (1968 Phys. Rev. 176 589). The plasmon dispersion results are found to be in very good agreement with the recent electron-energy-loss spectroscopy measurements by Nagao et al (2006 Phys. Rev. Lett. 97 116802). However, our predictions are found to depend strongly on the nature of the confinement model, the structure of the one-dimensional electronic band and the electron effective mass, implying a crucial role for the wire structure.

Dielectric response function and plasmon dispersion in a strongly coupled two-dimensional Coulomb liquid

We have formulated a dielectric response function for strongly coupled two-dimensional Coulomb liquids in the T=0 quantum domain. The formulation is based on the classical quasilocalized charge approximation [G. Kalman and K.I. Golden, Phys. Rev. A 41, 5516 (1990); K.I. Golden and G. Kalman, Phys. Plasmas 7, 14 (2000)] and extends the QLCA formalism into the quantum domain. We calculate the dispersion of the longitudinal plasmon mode for r(s) =10, 20, 40 and the resulting dispersion curves are compared with recent experimental results. We also conjecture the possible existence of a new high-wave-number collective excitation in close proximity to the right boundary of the pair continuum.