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Superconductivity in Films of Colloidal Nanocrystals. Ka Yee C. Lee, University of Chicago, DMR 0820054 . Fig. 1a (left) Image of the film of 20 nm Pb nanocrystals with oxide shell present, but organic ligands removed. Fig. 1b (right) The same film with shell converted to PbS .
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Superconductivity in Films of Colloidal Nanocrystals Ka Yee C. Lee, University of Chicago, DMR 0820054 Fig. 1a (left) Image of the film of 20 nm Pbnanocrystals with oxide shell present, but organic ligands removed. Fig. 1b (right) The same film with shell converted to PbS. Guyot-Sionnestand collaborators at the University of Chicago MRSEC developed a new method for the preparation of monodispersePbnanocrystals, Fig 1a. These particlesare covered with an oxide shell and organic ligands that prevent coupling between nanocrystals, where only the individual particles are superconducting [1]. Upon removal of the insulating shell, the coupling between particles is turned on, and the emergence of macroscopic superconductivity could be observed [2]. The insulating lead oxide shell could be easily converted to the more conductive lead sulfide, Fig 1b, and that this transformation reduced the resistance of the films by more than 10 orders of magnitude. Depending on the extent of the conversion, films show either insulating or metallic behavior at normal temperatures. Below the superconducting transition temperature, the insulating samples become “superinsulators” and show an exponential increase in resistance. 1. MeissnerEffect in Colloidal Pb Nanoparticles, P. Zolotavin, P. Guyot-Sionnest, ACS Nano 4, 5599-5608 (2010). 2. P. Guyot-Sionnest, et al., manuscript in preparation (2012).
