Quantum Dynamics of a Single Vortex

A special on recent results

composed by Andreas Wallraff

The first observation of the quantum dynamics of a single vortex in a superconductor ...
... quantum tunnelling and energy level quantization at millikelvin temperatures

We have performed experiments in which we have observed for the first time the quantum dynamics of a single Josephson vortex. Spectroscopically we have shown that the energy of a vortex in a potential well is quantized and that the vortex can tunnel through a potential barrier. These observations are important for the understanding of vortex properties at low temperatures in a wide range of systems such as superconductors, superfluids and atomic Bose condensates. They also have implications for the performance of superconducting devices which may be limited by the dynamics of vortices.

The results have been published in Nature on Sept 11, 2003:

Quantum Dynamics of a Single Vortex,
A. Wallraff, J. Lisenfeld, A. Lukashenko, A. Kemp, M. Fistul, Y. Koval and A. V. Ustinov,
Nature (London) 425, 155 (2003)
(reprint: Nature site - local pdf - local html )

The basic idea, our experimental findings and its implications presented for a popular audience

There is an accompanying news and views article written by John Clarke (Berkeley) in the same issue of Nature:

Vortices and hearts,
John Clarke,
Nature (London) 425, 133 (2003)
(reprint: Nature site - local pdf - local html)

Also, I have compiled a concise explanation of our experimental findings and its implications written for a non-specialist audience.

Additional References

For an introduction to the physics of Josephson vortices and some background information on the basic ideas of the experiments you may consult the following thesis (and the references therein):

Fluxon dynamics in annular Josephson junctions: From relativistic strings to quantum particles
A. Wallraff,
Mesoscopic Structures and Superconductivity 1,
Verlag: Lehrstuhl für Mikrocharakterisierung Universität Erlangen-Nürnberg (2001),
ISBN 3-932392-29-9
(pdf - also available as a book through any book store)

The experimental techniques used for the investigation of quantum tunnelling of a single vortex (and for quantum effects in current biased Josephson junctions in general) are described in a separate paper (and the references therein):

Switching current measurements of large area Josephson tunnel junctions
A. Wallraff, A. Lukashenko, C. Coqui, A. Kemp, T. Duty and A. V. Ustinov,
Review of Scientific Instruments, 74 3740 (2003)

The spectroscopic techniques used for the measurement of the energy level structure of a single vortex trapped in a potential well have been implemented and tested in measurements on current biased junctions in which we observed multi-photon transitions for the first time in this system. The results and the techniques used are described in the following paper and the references therein.

Multi-photon transitions between energy levels in a current-biased Josephson tunnel junction,
A. Wallraff, T. Duty, A. Lukashenko, and A. V. Ustinov,
Physical Review Letters 90, 037003 (2003)

A recent paper on the quantum dissociation of a vortex anti-vortex pair is available as a preprint

Quantum dissociation of a vortex-antivortex pair in a long Josephson junction,
M. V. Fistul, A. Wallraff, Y. Koval, A. Lukashenko, B. A. Malomed, and A. V. Ustinov,
submitted to Physical Review Letters (2003)

Additional references on vortex dynamics and the physics of Josephson junctions and its networks can be found on the publications section of the web page of the Erlangen group and in the publications section of my personal web page.