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Mesoscopic superconductor as a ballistic quantum switch

Nature volume 415, pages 60–62 (2002)Cite this article

Abstract

Several key experiments1,2,3 have revealed a rich variety of vortex structures in mesoscopic superconductors in which only a few quanta of magnetic flux are trapped: these structures are polygon-like vortex ‘molecules’ and multi-quanta giant vortices. Ginzburg–Landau calculations4 confirmed second-order phase transitions between the giant vortex states and stable molecule-like configurations5. Here we study theoretically the electronic structure and the related phase-coherent transport properties of such mesoscopic superconductor systems. The quasiparticle excitations in the vortices form coherent quantum-mechanical states that offer the possibility of controlling the phase-coherent transport through the sample by changing the number of trapped flux quanta and their configuration. The sample conductance measured in the direction of the applied magnetic field is determined by the transparency of multi-vortex configurations, which form a set of quantum channels. The transmission coefficient for each channel is controlled by multiple Andreev reflections within the vortex cores and at the sample edge. These interference phenomena result in a stepwise behaviour of the conductance as a function of the applied magnetic field, and we propose to exploit this effect to realize a vortex-based quantum switch where the magnetic field plays the role of the gate voltage.

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Figure 1: Phase-coherent transport through a few-flux-quanta superconductor.
Figure 2: Spatial distribution of the thermodynamically averaged local DOS g(r) normalized by its normal state value gN for multi-quanta vortices.
Figure 3: Spatial distribution of the thermodynamically averaged local DOS g(r) for a vortex molecule.
Figure 4: Energy spectrum for electronic states at the sample edge.

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Acknowledgements

We thank G. Crabtree, G. Karapetrov, A. Koshelev, V. Moshchalkov, D. A. Ryzhov, S. V. Sharov, I. A. Shereshevsky and I. D. Tokman for discussions. This work was supported by the US DOE Office of Science, a NATO Collaborative Linkage Grant, and by the Russian Foundation for Fundamental Research.

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Authors and Affiliations

  1. Institute for Physics of Microstructures, Russian Academy of Sciences, 603950, Nizhny Novgorod, GSP-105, Russia

    A. S. Mel'nikov

  2. Argonne National Laboratory, Argonne, 60439, Illinois, USA

    A. S. Mel'nikov & V. M. Vinokur

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  1. A. S. Mel'nikov
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  2. V. M. Vinokur
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Correspondence to V. M. Vinokur.

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Mel'nikov, A., Vinokur, V. Mesoscopic superconductor as a ballistic quantum switch. Nature 415, 60–62 (2002). https://doi.org/10.1038/415060a

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