Abstract
We present the theory of the Josephson effect in nanotube dots where an SU(4) symmetry can be realized. We find a remarkably rich phase diagram that significantly differs from the SU(2) case. In particular, -junction behavior is largely suppressed. We analytically obtain the Josephson current in various parameter regions: (i) in the Kondo regime covering the full crossover from SU(4) to SU(2), (ii) for weak tunnel couplings, and (iii) for a large BCS gap. The transition between these regions is studied numerically.
- Received 24 November 2009
DOI:https://doi.org/10.1103/PhysRevB.81.012502
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