M. Pi

Longitudinal modes of quantum dots in magnetic fields

Abstract.The far infrared longitudinal spin and density responses of two-dimensional quantum dots are discussed within local spin-density functional theory. The influence of a partial spin polarization, induced by a perpendicular static magnetic field, is taken into account in the coupling of spin and density channels. As an illustrative application, the case of a dot made of 5 electrons in parabolic confinement is discussed.We show that in the presence of massive particles such as nucleons, the standard low energy expansion in powers of meson momenta and light quark masses in general only converges in part of the low energy region. The expansion of the scalar form factor

Dissociation of Vertical Semiconductor Diatomic Artificial Molecules

\sigma(t)

Freezing of 4He and its liquid-solid interface from density functional theory

, for instance, breaks down in the vicinity of

Pinning of Quantized Vortices in Helium Drops by Dopant Atoms and Molecules

t=4M_\pi^2

STRUCTURE OF LARGE 3HE-4HE MIXED DROPS AROUND A DOPANT MOLECULE

. In the language of heavy baryon chiral perturbation theory, the proper behaviour in the threshold region only results if the multiple internal line insertions generated by relativistic kinematics are summed up to all orders. We propose a method that yields a coherent representation throughout the low energy region while keeping Lorentz and chiral invariance explicit at all stages. The method is illustrated with a calculation of the nucleon mass and of the scalar form factor to order

Electronic structure of few-electron concentric double quantum rings

p^4

The Structure and Energetics of 3He and 4He Nanodroplets Doped with Alkaline Earth Atoms

.

Communication: A combined periodic density functional and incremental wave-function-based approach for the dispersion-accounting time-resolved dynamics of 4He nanodroplets on surfaces: 4He/graphene

We investigate the dissociation of few-electron circular vertical semiconductor double quantum dot artificial molecules at 0 T as a function of interdot distance. A slight mismatch introduced in the fabrication of the artificial molecules from nominally identical constituent quantum wells induces localization by offsetting the energy levels in the quantum dots by up to 2 meV, and this plays a crucial role in the appearance of the addition energy spectra as a function of coupling strength particularly in the weak coupling limit.

Excited electron-bubble states in superfluid 4He: A time-dependent density functional approach

We show that, at high densities, fully variational solutions of solid-like type can be obtained from a density functional formalism originally designed for liquid 4He. Motivated by this finding, we propose an extension of the method that accurately describes the solid phase and the freezing transition of liquid 4He at zero temperature. The density profile of the interface between liquid and the (0001) surface of the 4He crystal is also investigated, and its surface energy evaluated. The interfacial tension is found to be in semiquantitative agreement with experiments and with other microscopic calculations. This opens the possibility to use unbiased DF methods to study highly non-homogeneous systems, like 4He interacting with strongly attractive impurities/substrates, or the nucleation of the solid phase in the metastable liquid.

Absorption spectrum of Ca atoms attached to 4He nanodroplets

Using a density functional method, we investigate the properties of liquid 4He droplets doped with atoms (Ne and Xe) and molecules ( SF6 and hydrogen cyanide). We consider the case of droplets having a quantized vortex pinned to the dopant. A liquid-drop formula is proposed that accurately describes the total energy of the complex and allows one to extrapolate the density functional results to large N. For a given impurity, we find that the formation of a dopant+vortex+(4)He(N) complex is energetically favored below a critical size N(cr). Our results support the possibility to observe quantized vortices in helium droplets by means of spectroscopic techniques.