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Abstract:

Switching, Tunneling, and Superconductivity in Percolating Cluster Films S. A. Brown1, A. Nande1, S. Fostner1, R. Gazoni1, A. Smith1, A. Sattar1, J. Grigg1, S. Couet2, K. Temst2, M.J. Van Bael3 1 The MacDiarmid Institute for Advanced Materials and Nanotechnology, Dept. of Physics and Astronomy, University of Canterbury, 8140, Christchurch, New Zealand 2 Instituut voor Kern- en Stralingsfysica, Celestijnenlaan 200 D, KU Leuven, Leuven B-3001, Belgium 3 Laboratory of Solid State Physics and Magnetism, Celestijnenlaan 200 D, KU Leuven, Leuven B-3001, Belgium When clusters are randomly deposited on a surface they produce percolating films which have remarkable electrical properties.[1] Here we will focus on devices that contain percolating films of Sn and Pb clusters between a pair of electrical contacts, and especially those that are deliberately constructed so as to guarantee that the film is close to the percolation threshold (onset of conduction). In these devices quantum mechanical tunnelling is important[2], and several new and unexpected phenomena are observed. In particular we have recently demonstrated switching between well-defined, quantized, conductance values [multiples of the quantum of conductance (2e2/h)], at room temperature.[3] Recently we have begun exploring the superconducting properties of these films. We find that the percolating films have interesting characteristics that are intermediate between those of 1D and 2D systems. We will discuss phase slips[4,5], which appear to occur in the narrow necks between clusters, and the competition between percolation and the Berenzinski-Kosterlitz-Thouless transition[6,7]. We will also discuss a superconductor to insulator transition which can be driven by the applied current. [1] J. Schmelzer jr, S. A. Brown, A. Wurl, M. Hyslop, and R. J. Blaikie, Phys. Rev. Lett. 88, 226802 (2002). [2] S. Fostner, R. Brown, J. Carr, and S. A. Brown, Phys. Rev. B 89, 075402 (2014). [3] A. Sattar, S. Fostner, and S. A. Brown, Phys. Rev. Lett. 111, 136808 (2013). [4] A. Nande et al, to be published. [5] J. S. Langer and Vinay Ambegaokar, Physical Review 164, 498 (1967); W. A. Little, Physical Review 156, 396 (1967). [6] V. L. Berezinskii, Sov. Phys. JETP 34, 610 (1972); J. M. Kosterlitz and D. J. Thouless, J. Phys. C 6, 1181 (1973). [7] S. Fostner et al, to be published.