Spontaneous Coherence and Collective Modes in Double-Layer Quantum Dot Systems

We study the ground state and the collective excitations of parabolically-confined double-layer quantum dot systems in a strong magnetic field. We identify parameter regimes where electrons form maximum density droplet states, quantum-dot analogs of the incompressible states of the bulk integer quantum Hall effect. In these regimes the Hartree-Fock approximation and the time-dependent Hartree-Fock approximations can be used to describe the ground state and collective excitations respectively. We comment on the relationship between edge excitations of dots and edge magneto-plasmon excitations of bulk double-layer systems.Comment: 20 pages (figures included) and also available at http://fangio.magnet.fsu.edu/~jhu/Paper/qdot_cond.ps, replaced to fix figure

CARBON POWDER MAGNETIZATION THERMOMETRY FOR VERY LOW TEMPERATURES

Nous avons étudié l'aimantation statique d'un noir de carbone amorphe (Carbolac I) en fonction de la température en vue d' utiliser ce matériau comme thermomètre à basse température. Nous trouvons que l'aimantation suit une loi de Curie au-dessus de 10 mK. Les mesures, effectuées dans une série de champs magnétiques, suggèrent un système paramagnétique de spin 1 ayant un facteur g égal à 2.We have investigated the temperature dependent static magnetization of an amorphous carbon black (Carbolac I) for use as a low temperature secondary thermometer. We find that the magnetization obeys Curie's law above 10 mK. Measurements performed in a number of magnetic fields are consistent with a spin I paramagnetic system with a g-factor of 2