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Articles 31 - 32 of 32
Full-Text Articles in Physics
Spin Uncoupling In Free Nb Clusters: Support For Nascent Superconductivity, Ramiro Moro, Shuangye Yin, Xiaoshan Xu, Walt A. De Heer
Spin Uncoupling In Free Nb Clusters: Support For Nascent Superconductivity, Ramiro Moro, Shuangye Yin, Xiaoshan Xu, Walt A. De Heer
Xiaoshan Xu Papers
Molecular beam Stern-Gerlach deflection measurements on Nb clusters (NbN, N <100) show that at very low temperatures the odd-N clusters deflect due to a single unpaired spin that is uncoupled from the cluster. At higher temperatures the spin is coupled and no deflections are observed. Spin uncoupling occurs concurrently with the transition to the recently found ferroelectric state, which has superconductor characteristics [Science 300, 1265 (2003)]. Spin uncoupling (also seen in V, Ta, and Al clusters) is analogous to the reduction of spin-relaxation rates observed in bulk superconductors below Tc.
Ferroelectricity In Free Niobium Clusters, Ramiro Moro, Xiaoshan Xu, Shuangye Yin, Walt A. De Heer
Ferroelectricity In Free Niobium Clusters, Ramiro Moro, Xiaoshan Xu, Shuangye Yin, Walt A. De Heer
Xiaoshan Xu Papers
Electric deflections of gas-phase, cryogenically cooled, neutral niobium clusters [NbN; number of atoms (N) = 2 to 150, temperature (T) = 20 to 300 kelvin], measured in molecular beams, show that cold clusters may attain an anomalous component with very large electric dipole moments. In contrast, room-temperature measurements show normal metallic polarizabilities. Characteristic energies kBTG(N) [Boltzmann constant kB times a transition temperature TG(N)] are identified, below which the ferroelectric-like state develops. Generally, TG decreases [110 > TG(N) > 10K] as …