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Superconductivity in reduced dimensions :-
When the diameter of a superconducting wire is smaller than the phase coherence length, its behavior is expected to deviate from that of bulk and crosses over towards that expected of a one-dimensional system. This project aims to elucidate the properties of quasi-one-dimensional superconducting nanowires by studying their transport and thermodynamic properties. The nanowires are fabricated by means of electrodeposition into porous membrane with the pores aligned as one dimensional non-intersecting channels [1]. Transport measurements on Sn nanowires with diameter of 20 and 40 nm show a resistive tail extending down to 0.47K and the residual resistance is found to be ohmic [2]. Recently, we found an intriguing anti-proximity effect for Zn wires sandwiched between two bulk superconducting electrodes. It was found that the superconductivity of Zn nanowires of diameter 40 nm is suppressed either completely or partially by the superconducting electrodes. When the electrodes are driven into their normal state by a magnetic field, the nanowires switch back to their superconducting state [3]. Current effort on this project aims to understand how universal is this phenomenon and to carry out four lead measurements on these thin wires. This project is supported by the Center for Nanoscale Science (Penn State MRSEC) and it is a collaboration with the research groups of Tom Mallouk (Chemistry), Theresa Mayer (EE) and Jinguo Wang (MRI).
[1] M. Tian, J. Wang, J. S. Kurtz, T.E. Mallouk and M.H.W. Chan, Nano Lett. 3, 919 (2003) [2] M. Tian et.al., Phys. Rev. B 71, 104521 (2005) [3] M. Tian, N. Kumar, S. Xu, J. Wang, J. Kurtz and M.H.W. Chan, Phys. Rev. Lett. 95, 076802 (2005) |
