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Tuning the Quantum Stability and Superconductivity of Ultrathin Metal Alloys

Ge( ). Pb(3×3). Tuning the Quantum Stability and Superconductivity of Ultrathin Metal Alloys. M. M. Ozer 1 , Y. Jia 2 , J. R. Thompson 1 , Z. Y. Zhang 1,3 , H. H. Wertering 1,3. 1 Department of Physics & Astronomy, The University of Tennessee

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Tuning the Quantum Stability and Superconductivity of Ultrathin Metal Alloys

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  1. Ge( ) Pb(3×3) Tuning the Quantum Stability and Superconductivity of Ultrathin Metal Alloys M. M. Ozer1, Y. Jia2, J. R. Thompson1, Z. Y. Zhang1,3, H. H. Wertering1,3 1Department of Physics & Astronomy, The University of Tennessee 2School of Physics and Engineering, Zhengzhou University, China 3 Materials Science & Technology Division, Oak Ridge National Laboratory Motivation Quantum confinement of itinerant electrons in atomically-smooth ultrathin Pb films produces strong oscillations in the thickness-dependent film energy. By adding extra electrons via bismuth alloying, we show that both the structural stability and superconducting properties of such films can be tuned. The phase boundary (upper critical field) between the superconducting vortex state and normal state indicates an anomalous suppression of superconducting order just below the critical temperature Tc. This suppression varies systematically with the film thickness and Bi content and can be parametrized in terms of a characteristic temperature Tc* < Tc that is inversely proportional to the scattering mean free path. The results indicate that the isotropic superconductive pairing in bulk PbBi alloys is non-trivially modified in the quantum regime **The Quantum Size Effect of PbBi Ultrathin Metal Alloys** ▼Calculated surface energy of a PbBi free-standing alloy slab. The black curve (circles) and red curve (squares) represent the surface energy for maximum and minimum Bi-Bi separation in the film growth direction. Experiment ◄Surface energy of a PbBi alloy on a Si(111) substrate, with the inset showing its second derivative versus film thickness. Theory ▲STM images revealing the quantum growth mode of PbBi alloy films with bilayer growth Stable layer: 4-6-7-9-11-13-15-17-19-20-22-24-26…..

  2. ***Tuning the Superconductivity of Ultrathin Metal Alloys*** Summary Supported by NSF of China, NSF of USA and USDOE

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