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Current-Phase Relation of Ballistic Graphene Josephson Junctions.
G Nanda1, J L Aguilera-Servin1,2, P Rakyta3
1Kavli Institute of Nanoscience, Delft University of Technology , 2600 GA Delft, The Netherlands.
Nano Letters
|May 6, 2017
Summary
We determined the current-phase relation (CPR) of graphene Josephson junctions (JJs) using a tunable superconducting quantum interference device (SQUID). The CPR was found to be skewed and tunable with gate voltage.
Area of Science:
- Condensed matter physics
- Quantum electronics
- Materials science
Background:
- The current-phase relation (CPR) describes supercurrent behavior in Josephson junctions (JJs), crucial for understanding JJ responses.
- Graphene-based JJs are of increasing interest, but their CPRs are largely unknown.
Purpose of the Study:
- To determine the CPR of ballistic graphene JJs.
- To investigate the tunability of the CPR using gate voltage.
Main Methods:
- Fabrication of a fully gate-tunable graphene superconducting quantum interference device (SQUID) with encapsulated JJs.
- Independent control of critical currents for symmetric/asymmetric SQUID operation.
- Directly obtaining CPR by phase-biasing a JJ in an asymmetric SQUID configuration.
Main Results:
- The CPR of ballistic graphene JJs was directly measured and found to be significantly skewed from a sinusoidal form.
- The CPR skewness is tunable via gate voltage.
- The skewness exhibits oscillations in antiphase with Fabry-Pérot resistance oscillations.
Conclusions:
- The study provides the first direct measurement of the CPR for ballistic graphene JJs.
- The findings highlight the tunability of graphene JJ properties and their potential for quantum devices.
- Experimental results show good qualitative agreement with theoretical tight-binding calculations.
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