Collective spin excitations of alkali-metal clusters

We study spin collective modes in paramagnetic systems using a sum rule approach. We give a simple and analytical expression for the static magnetic polarizability of finite size systems in terms of their radii and of the magnetic susceptibility of a uniform system. A systematics for the mean excitation energy of spin modes in clusters and shells is given. In metal spheres, the hydrodynamical model is solved and compared with the sum rule approach. An estimate for the mean excitation energy of the spin dipole collective state in fullerene is given.

Section: Introductionsupporting

confidence: 78%

Section: The Sum Rule Approachsupporting

confidence: 62%

A sum rule approach to collective spin modes in paramagnetic clusters, cavities and shells

Lipparini

Califano

1996

“…This is due to the fact that the residual interaction in the spin channel is attractive and much smaller than in the dipole channel. The spectra agree with the results of a linearized calculation as it was investigated in [10], although obtained with a slightly different density functional. Figure 2 shows the power spectra for Na> excited in the multi-plasmon regime at about 12 eV.…”

Section: Resultssupporting

confidence: 79%

“…The enhanced number of degrees-of-freedom could lead to more dissipative effects than in spinless electron dynamics, particularly in the nonlinear regime. Spin modes in metal clusters within a linearized TDLDA have been studied in [10]. The strongly collective spin mode, however, appears at much lower energy than the Mie plasmon because the residual interaction in the spin channel is attractive in contrast to the normal dipole channel.…”

Section: Introductionmentioning

confidence: 99%

Spin dynamics in sodium clusters

Mornas

Calvayrac

Suraud

et al. 1996

We investigate the dynamics of the electron cloud in a metal cluster from the regime of small oscillations up to high excitations in the multi-plasmon regime. Particular attention is paid to the effect of spin modes. Test cases are a spin saturated cluster, Na >, and a strongly spin polarized cluster, the spherical isomer of Na >. The spectral distributions are dominated by the Mie plasmon resonance and a strong collective spin mode in all cases considered. Nonlinear effects as cross talk between multi-plasmon states or chaotic pattern cannot be observed in the investigated energy range.

“…The analysis in [8] was done by starting from the Gunnarsson-Lundqvist energy functional [9] considering only spin S"0 modes. Low-lying collective S"1 excitations in metal clusters have been predicted in [10] within the Time-Dependent Local-Spin-Density Approximation (TDLSDA) based on the Vosko, Wilk and Nusair (VWN) energy functional [11]. In order to assess how much the inclusion of such collective excitations modifies the ground state properties, in the present paper we extend the analysis of [8] by considering both S"0 and S"1 modes and using the VWN energy functional.…”

Section: Introductionmentioning

confidence: 99%

Ground state correlations of jellium metal clusters in local spin-density approximation

Catara

Serra

Giai

1997

The role of S"1 excitations on the ground state of jellium clusters is analyzed within the randomphase approximation (RPA). The importance of the correlation-energy contribution to the residual interaction in this channel, in order to obtain a consistent description of the cluster electronic states, is stressed. The modification of the single-particle occupation numbers in the RPA ground state is obtained. This modification is found too large when considering only Coulomb exchange contributions to the functional, which clearly points the inadequacy of RPA for this approximate functional and the necessity to include correlation-energy contributions.