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Order Parameter of a Nanometre-Scale S-Wave Superconducting Grain in Quantum Tunnelling Process: Frequency Space Analysis |
| R. Afzali1;A. T. Rezakhani2,3 |
| 1Department of Physics, Faculty of Science, University of Isfahan, 81744 Isfahan, Iran
2Institute for Scientific Interchange, Villa Gualino, Viale Settimio Severo 65, I-10133 Torino, Italy
3Institute for Quantum Information Science, University of Calgary, Alberta T2N 1N4, Canada |
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| Cite this article: |
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R. Afzali, A. T. Rezakhani 2006 Chin. Phys. Lett. 23 967-970 |
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Abstract A nano-scale $s$-wave superconducting grain, coupled to a normal metallic contact through a tunnelling junction, is placed in an external magnetic field. We suppose that effect of this quantum tunnelling on the Fourier transform of the order parameter is in the form of a small additive correction to the BCS order parameter. At the first order approximation in terms of this correction term and by using an instanton method, the related Green functions (in frequency space) are obtained. By establishing a self-consistent configuration an analytic formula for the order parameter is also found. We also show that a departure from superconductivity can be captured by this formula. This change of state is indeed a manifestation of a quantum transition induced by quantum fluctuations. In this sense, this is an advantage of our simple method which, like other more elaborate methods, can detect a quantum transition in the state of the grain.
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| Keywords:
74.40.+k
73.63.-b
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Published: 01 April 2006
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| PACS: |
74.40.+k
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73.63.-b
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(Electronic transport in nanoscale materials and structures)
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