Antonios Balassis

Anisotropic plasmon-coupling dimerization of a pair of spherical electron gases

We have discovered a novel feature in the plasmon excitations for a pair of Coulomb-coupled non-concentric spherical two-dimensional electron gases (S2DEGs). Our results show that the plasmon excitations for such pairs depend on the orientation with respect to the external electromagnetic probe field. The origin of this anisotropy of the inter-sphere Coulomb interaction is due to the directional asymmetry of the electrostatic coupling of electrons in excited states which depend on both the angular momentum quantum number L and its projection M on the axis of quantization taken as the probe E-field direction. We demonstrate the anisotropic inter-sphere Coulomb coupling in space and present semi-analytic results in the random-phase approximation both perpendicular and parallel to the axis of quantization. For the incidence of light with a finite orbital or spin angular momentum, the magnetic field generated from an induced oscillating electric dipole on one sphere can couple to an induced magnetic dipole on another sphere in a way that is dependent on whether the direction is parallel or perpendicular to the probe E field. Such an effect from the plasmon spatial correlation is expected to be experimentally observable by employing circularly polarized light or a helical light beam for incidence. The S2DEG serves as a simple model for fullerenes as well as metallic dimers, when the energy bands are far apart.

Strongly Localized Image States of Spherical Graphitic Particles

We investigate the localization of charged particles by the image potential of spherical shells, such as fullerene buckyballs. These spherical image states exist within surface potentials formed by the competition between the attractive image potential and the repulsive centripetal force arising from the angular motion. The image potential has a power law rather than a logarithmic behavior. This leads to fundamental differences in the nature of the effective potential for the two geometries. Our calculations have shown that the captured charge is more strongly localized closest to the surface for fullerenes than for cylindrical nanotube.

A half-step in quantized conductance for low-density electrons in a quantum wire

We investigated the effect of perpendicular magnetic field on quantum wires when the spin-orbit interaction (SOI) of electrons is not neglected. Based on the calculated energy dispersion, the nonlinear ballistic conductance (G) and electron-diffusion thermoelectric power (Sd) are calculated as functions of the electron density, temperature and applied bias voltage. A low-temperature half-step feature in G that was observed experimentally by Quay et al. [Nat. Phys. 6, 336 (2010)], as well as a new peak in Sd are reproduced here in the low density region. These phenomena are related to the occurrence of Zeeman splitting and a SOI induced saddle point in the band structure where the channel chemical potential lies within an anticrossing gap between the saddle point of the lower subband and the bottom of the upper subband. Additionally, side peaks in G that are far away from the zero bias for the nonlinear transport, as well as a quadratic bias-voltage dependence of G near zero voltage, are predicted and disc...

Ab initio calculation of low-energy collective charge-density excitations in MgB2

We present ab initio time-dependent density-functional theory calculation results for low-energy collective electron excitations in

Thermal smearing and screening in a strong magnetic field for Dirac materials in comparison with the two dimensional electron liquid

{text{MgB}}_{2}

Energy bands, conductance, and thermoelectric power for ballistic electrons in a nanowire with spin-orbit interaction

. The existence of a long-lived collective excitation corresponding to coherent charge density fluctuations between the boron

Enhanced response of current-driven coupled quantum wells

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Combined effect of doping and temperature on the anisotropy of low-energy plasmons in monolayer graphene

and

Plasmons in a superlattice of fullerenes or metallic shells

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Current-driven plasma instabilities for a bilayer two-dimensional electron system

bands (