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Josephson junction with a magnetic-field tunable ground state.
E Goldobin1, D Koelle, R Kleiner
1Physikalisches Institut and Center for Collective Quantum Phenomena in LISA, Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany.
Physical Review Letters
|December 21, 2011
Summary
This study explores asymmetric 0-π Josephson junctions, revealing a tunable ground state in a magnetic field. The critical current dependence on the field offers experimental methods to observe this unique Josephson junction behavior.
Area of Science:
- Condensed Matter Physics
- Quantum Electronics
- Superconductivity
Background:
- Asymmetric 0-π Josephson junctions exhibit unique quantum properties due to competing 0 and π superconducting states.
- The effective sine-Gordon equation describes the spatially averaged phase (ψ) in these junctions.
- A negative second harmonic in the current-phase relation can lead to a doubly degenerate ground state (ψ=±φ).
Purpose of the Study:
- To investigate the behavior of asymmetric 0-π Josephson junctions in an applied magnetic field (H).
- To determine how a magnetic field influences the junction's effective current-phase relation and ground state.
- To identify experimental methods for observing the tunable ground state.
Main Methods:
- Modeling the asymmetric 0-π Josephson junction using an effective sine-Gordon equation.
- Analyzing the impact of an applied magnetic field (H) on the current-phase relation.
- Investigating the dependence of the critical current on the magnetic field.
Main Results:
- An applied magnetic field (H) introduces an additional term (∝Hcosψ) into the effective current-phase relation.
- This magnetic field term results in a nontrivial ground state that is tunable by the magnetic field.
- The critical current's dependence on H provides a means to experimentally probe the ground state.
Conclusions:
- Asymmetric 0-π Josephson junctions exhibit a magnetic-field-tunable ground state.
- The interplay between intrinsic junction properties and external magnetic fields is crucial for controlling quantum states.
- Experimental measurements of critical current versus magnetic field can confirm the predicted ground state properties.
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