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Science 23 May 2003:
Vol. 300. no. 5623, pp. 1265 - 1269
DOI: 10.1126/science.1083247
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Reports

Ferroelectricity in Free Niobium Clusters

Ramiro Moro, Xiaoshan Xu, Shuangye Yin, Walt A. de Heer

Electric deflections of gas-phase, cryogenically cooled, neutral niobium clusters [NbN; number of atoms (N) = 2 to 150, temperature (T) = 20to 300kelvin], 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 N increases, with pronounced even-odd alternations for N > 38. This new state of metallic matter may be related to bulk superconductivity.

School of Physics, Georgia Institute of Technology, Atlanta GA, 30332–0430, USA.

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Science. ISSN 0036-8075 (print), 1095-9203 (online)