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Chaotic dynamics from coupled magnetic monodomain and Josephson current
A E Botha1, Yu M Shukrinov2,3,4, J Tekić5
1Department of Physics, University of South Africa, Private Bag X6, Roodepoort, Johannesburg 1710, South Africa.
Physical Review. E
|March 18, 2023
Summary
Superconductor-ferromagnet-superconductor Josephson junctions exhibit chaotic dynamics due to magnetic layer degrees of freedom. Chaos onset occurs before the superconducting state transition, indicated by supercurrent rise and phase rotation anharmonicity.
Area of Science:
- Condensed Matter Physics
- Nonlinear Dynamics
- Spintronics
Background:
- Standard superconductor-insulator-superconductor Josephson junctions lack chaos without external AC drive.
- Superconductor-ferromagnet-superconductor (φ₀) junctions possess extra degrees of freedom from magnetic layers, enabling complex dynamics.
Purpose of the Study:
- Investigate chaotic dynamics in φ₀ Josephson junctions.
- Explore transitions between quasiperiodic, chaotic, and regular states.
- Analyze synchronization properties and onset of chaos.
Main Methods:
- Utilized the Landau-Lifshitz-Gilbert model for magnetic moments.
- Employed the resistively capacitively shunted-junction model for Josephson junctions.
- Analyzed chaotic dynamics near ferromagnetic resonance.
- Computed Lyapunov characteristic exponents and bifurcation diagrams (one-parameter and two-dimensional).
Main Results:
- Two Lyapunov exponents are trivially zero due to magnetic moment conservation.
- Bifurcation diagrams reveal transitions to chaos as DC-bias current (I) is varied.
- Chaos onset precedes the transition to the superconducting state.
- Supercurrent rise and increasing phase rotation anharmonicity signal chaos.
Conclusions:
- φ₀ Josephson junctions can exhibit intrinsic chaotic dynamics.
- The interplay between Josephson and magnetic energies governs system behavior.
- Chaos is a precursor to the superconducting state transition in these systems.
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