9,773 research outputs found
Orbital magnetism in axially deformed sodium clusters: From scissors mode to dia-para magnetic anisotropy
Low-energy orbital magnetic dipole excitations, known as scissors mode (SM),
are studied in alkali metal clusters. Subsequent dynamic and static effects are
explored. The treatment is based on a self-consistent microscopic approach
using the jellium approximation for the ionic background and the Kohn-Sham mean
field for the electrons. The microscopic origin of SM and its main features
(structure of the mode in light and medium clusters, separation into low- and
high-energy plasmons, coupling high-energy M1 scissors and E2 quadrupole
plasmons, contributions of shape isomers, etc) are discussed. The scissors M1
strength acquires large values with increasing cluster size. The mode is
responsible for the van Vleck paramagnetism of spin-saturated clusters. Quantum
shell effects induce a fragile interplay between Langevin diamagnetism and van
Vleck paramagnetism and lead to a remarkable dia-para anisotropy in magnetic
susceptibility of particular light clusters. Finally, several routes for
observing the SM experimentally are discussed.Comment: 21 pages, 7 figure
Transition Temperature for Weakly Interacting Homogeneous Bose Gases
We apply the nonperturbative optimized linear δ expansion method to the O(N) scalar field model in three dimensions to determine the transition temperature of a dilute homogeneous Bose gas. Our results show that the shift of the transition temperature ΔTc/Tc of the interacting model, compared with the ideal-gas transition temperature, really behaves as γan1/3 where a is the s-wave scattering length and n is the number density. For N=2 our calculations yield the value γ=3.059
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