Spectroscopy of a fractional Josephson vortex molecule

Abstract

In long Josephson junctions with multiple discontinuities of the Josephson phase, fractional vortex molecules are spontaneously formed. At each discontinuity point a fractional Josephson vortex carrying a magnetic flux $|\Phi |<{\Phi }_0$, ${\Phi }_0\approx 2.07\times 10^{-15}$ Wb being the magnetic flux quantum, is pinned. Each vortex has an oscillatory eigenmode with a frequency that depends on $\Phi /{\Phi }_0$ and lies inside the plasma gap. We experimentally investigate the dependence of the eigenfrequencies of a two-vortex molecule on the distance between the vortices, on their topological charge $\wp =2\pi \Phi /{\Phi }_0$ and on the bias current $\gamma$ applied to the Josephson junction. We find that with decreasing distance between vortices, a splitting of the eigenfrequencies occurs, that corresponds to the emergence of collective oscillatory modes of both vortices. We use a resonant microwave spectroscopy technique and find good agreement between experimental results and theoretical predictions.

submitted to Phys. Rev. B

References in corpus (14)

• 0-pi Josephson tunnel junctions with ferromagnetic barrier
• Josephson junctions with negative second harmonic in the current-phase relation: properties of novel varphi-junctions
• Dynamics of semifluxons in Nb long Josephson 0-pi junctions
• Semi-fluxons in long Josephson 0-pi-junctions
• Quantum tunneling of semifluxons
• Ground states of one and two fractional vortices in long Josephson 0-kappa-junctions
• Fluxon-semifluxon interaction in an annular long Josephson 0-pi-junction
• Spectroscopy of the fractional vortex eigenfrequency in a long Josephson 0-kappa junction
• Oscillatory eigenmodes and stability of one and two arbitrary fractional vortices in long Josephson 0-kappa-junctions
• Non-ideal artificial phase discontinuity in long Josephson 0-kappa-junctions
• Semifluxon molecule under control
• Aluminum Hard Mask Technique for the Fabrication of High-Quality Submicron Nb/Al-AlOx/Nb Josephson Junctions
• Ac-induced thermal vortex escape in magnetic-field-embedded long annular Josephson junctions
• On the Classical Model for Microwave Induced Escape from a Josephson Washboard Potential

Cited by in corpus (3)

• Sub-μm Josephson Junctions for Superconducting Quantum Devices
• Superconductors that do not expel magnetic flux
• A tunable macroscopic quantum system based on two fractional vortices