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Science 15 June 2007:
Vol. 316. no. 5831, pp. 1594 - 1597
DOI: 10.1126/science.1142159
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Reports

Tuning the Quantum Stability and Superconductivity of Ultrathin Metal Alloys

Mustafa M. Özer,1* Yu Jia,2 Zhenyu Zhang,3,1 James R. Thompson,1,3 Hanno H. Weitering1,3{dagger}

Quantum confinement of itinerant electrons in atomically smooth ultrathin lead films produces strong oscillations in the thickness-dependent film energy. By adding extra electrons via bismuth alloying, we showed that both the structural stability and the superconducting properties of such films can be tuned. The phase boundary (upper critical field) between the superconducting vortex state and the normal state indicates an anomalous suppression of superconducting order just below the critical temperature, Tc. This suppression varies systematically with the film thickness and the bismuth content and can be parametrized in terms of a characteristic temperature, Tc* (less than Tc), that is inversely proportional to the scattering mean free path. The results indicate that the isotropic nature of the superconductive pairing in bulk lead-bismuth alloys is altered in the quantum regime.

1 Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, USA.
2 School of Physics and Engineering, Zhengzhou University, Zhengzhou, Henan, 450052, China.
3 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.

* Present address: Department of Physics, University of Texas, Austin, TX 78712, USA.

{dagger} To whom correspondence should be addressed. E-mail: hanno{at}utk.edu

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Superconductivity at the Two-Dimensional Limit.
S. Qin, J. Kim, Q. Niu, and C.-K. Shih (2009)
Science 324, 1314-1317
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Science. ISSN 0036-8075 (print), 1095-9203 (online)