Two-dimensional Josephson vortex lattice and anomalously slow decay of the Fraunhofer oscillations in a ballistic SNS junction with a warped Fermi surface
| Autor: | Ostroukh, V. P., Baxevanis, B., Akhmerov, A. R., Beenakker, C. W. J. |
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| Rok vydání: | 2016 |
| Předmět: | |
| Zdroj: | Phys. Rev. B 94, 094514 (2016) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1103/PhysRevB.94.094514 |
| Popis: | $ $The critical current of a Josephson junction is an oscillatory function of the enclosed magnetic flux $\Phi$, because of quantum interference modulated with periodicity $h/2e$. We calculate these Fraunhofer oscillations in a two-dimensional (2D) ballistic superconductor--normal-metal--superconductor (SNS) junction. For a Fermi circle the amplitude of the oscillations decays as $1/\Phi$ or faster. If the Fermi circle is strongly warped, as it is on a square lattice near the band center, we find that the amplitude decays slower $\propto 1/\sqrt\Phi$ when the magnetic length $l_m=\sqrt{\hbar/eB}$ drops below the separation $L$ of the NS interfaces. The crossover to the slow decay of the critical current is accompanied by the appearance of a 2D array of current vortices and antivortices in the normal region, which form a bipartite rectangular lattice with lattice constant $\simeq l_m^2/L$. The 2D lattice vanishes for a circular Fermi surface, when only the usual single row of Josephson vortices remains. Comment: 12 pages, 14 figures; V2: added three appendices, including data on the superconducting order parameter and density of states |
| Databáze: | arXiv |
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