Switchable Josephson Junction Using Ferromagnetic Insulators
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Solution Overview
Problem
Existing Josephson junctions lack efficient control over Josephson tunneling between superconducting layers, particularly in magnetic inter-layers, which limits their applications in superconducting spintronics and quantum computing due to uncontrolled switching between super- and normal currents.
Innovation Solution
The use of ferromagnetic insulators with controlled magnetic alignments to sandwich a superconducting layer, allowing Josephson tunneling to be switched between superconducting and normal states by adjusting the relative magnetization orientation of the ferromagnetic insulators, thereby controlling the interfacial exchange field and the superconducting state of the junction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ferromagnetic insulators with controlled magnetic alignments are used to sandwich a superconducting layer, then Josephson tunneling can be switched between superconducting and normal states, but the device complexity increases due to the multi-layer structure
Solution Approach 1:
The device is segmented into distinct functional layers: ferromagnetic insulator layers (with controlled magnetic alignments) and superconducting layers. This segmentation allows independent optimization of each layer's properties and enables reliable switching by controlling the relative magnetization orientation of the ferromagnetic insulators, while the modular structure facilitates fabrication and integration.
Solution Approach 2:
The invention employs composite material structures combining ferromagnetic insulators and superconductors. The ferromagnetic insulator layers provide magnetic control without dissipating supercurrent, while the superconducting layers enable lossless current transport. This composite approach achieves reliable switching between superconducting and normal states through interfacial exchange coupling, with the magnetic alignment controlling the Josephson tunneling behavior.
2Ease of operation
If external magnetic fields are used to control Josephson tunneling, then switching between states is achieved, but energy consumption increases and control precision decreases
Solution Approach 1:
The ferromagnetic insulator layers possess stable, controlled magnetic alignments that inherently generate the necessary exchange fields at the superconductor-ferromagnet interfaces. This self-service mechanism eliminates the need for external magnetic fields or additional control components, achieving precise control of Josephson tunneling without energy consumption. The relative magnetization orientation of the ferromagnetic insulators directly determines the superconducting state.
Solution Approach 2:
The ferromagnetic insulator layers act as intermediaries that translate magnetic alignment configurations into controlled exchange fields at the interfaces with superconducting layers. This intermediary mechanism provides precise control over Josephson tunneling by mediating the interaction between magnetic order and superconductivity, avoiding the need for direct external field application and enabling energy-efficient switching.
3Adaptability or versatility
If magnetic inter-layers are used in Josephson junctions, then applications in superconducting spintronics and quantum computing are enabled, but uncontrolled switching between super- and normal currents occurs
Solution Approach 1:
The ferromagnetic insulator layers are positioned specifically at the interfaces with superconducting layers, where they locally generate exchange fields that control the superconducting state. This localized control mechanism enables reliable switching between superconducting and normal states at specific regions without affecting the entire device, achieving both application versatility in superconducting spintronics and quantum computing and reliable current control.
Solution Approach 2:
The invention controls the superconducting state by changing the magnetic alignment parameter of the ferromagnetic insulator layers. By adjusting the relative magnetization orientation (parallel or antiparallel alignment) of the ferromagnetic insulators, the exchange field at the interfaces is modulated, which directly controls the Josephson tunneling behavior. This parameter control mechanism enables reliable switching while maintaining stability, supporting diverse applications in superconducting spintronics and quantum computing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables reliable and reproducible switching between superconducting and normal states, enhancing the functionality of Josephson junctions for applications in superconducting spintronics and quantum computing by passively controlling the Josephson tunneling behavior without the need for external magnetic fields.
Implementation Method 1
Josephson tunneling occurs between the first superconducting layer and second superconducting layer across one of the ferromagnetic layers
Implementation Method 2
the conductive state is controlled by the relative magnetization orientation of the ferromagnetic insulators where the first superconducting layer is superconducting when the two magnetizations are aligned in antiparallel but it turns normally conducting when the magnetic alignment is parallel
Data Source
AI summary
A switchable Josephson junction is provided that includes a plurality of ferromagnetic insulators that are defined by their respective magnetic alignments. A first superconducting layer that is positioned between any two of the ferromagnetic insulators, wherein the conductive state is controlled by the relative magnetization orientation of the ferromagnetic insulators where the first superconducting layer is superconducting when the two magnetizations are aligned in antiparallel but it turns normally conducting when the magnetic alignment is parallel. A second superconducting layer is adjacent one of the ferromagnetic layers, wherein Josephson tunneling occurs between the first superconducting layer and second superconducting layer across one of the ferromagnetic layers.