Graphene Josephson Oscillator With Gate-Tuned Cryogenic Frequency
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Solution Overview
Problem
There is a need for a tunable microwave or millimeter wave oscillator that can be used in cryogenic computing applications, requiring a system capable of modifying its oscillation frequency effectively.
Innovation Solution
A system comprising a Josephson junction formed by a graphene channel between two superconducting terminals, with a conductive gate that modifies the oscillation frequency by applying a voltage, and additional components such as bias circuits, a graphene sandwich, and a substrate for operation at cryogenic temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional oscillator design is used, then the structure is simple and easy to manufacture, but the oscillation frequency cannot be tuned or adjusted
Solution Approach 1:
The patent applies the dynamics principle by introducing a gate electrode that can dynamically adjust the oscillation frequency of the Josephson junction oscillator. The gate voltage can be varied to tune the frequency, transforming a static oscillator into a dynamically adjustable one. This resolves the contradiction by enabling frequency tunability while maintaining a relatively simple planar structure.
Solution Approach 2:
The patent employs parameter changes by modifying the electrical parameters of the Josephson junction through gate voltage control. By changing the gate voltage, the critical current and oscillation frequency parameters are adjusted, enabling continuous frequency tuning. This approach achieves adaptability without requiring complex mechanical or structural modifications.
2Speed
If the gap between superconducting terminals is made smaller, then the critical current increases, but the oscillation frequency decreases
Solution Approach 1:
The patent resolves this contradiction by using gate voltage to independently control the oscillation frequency without changing the physical gap dimensions. By applying different gate voltages, the frequency can be tuned from 24 GHz to 100 GHz while maintaining a fixed gap size, thus preserving the critical current while achieving frequency adjustment.
Solution Approach 2:
The dynamic control of oscillation frequency through gate voltage allows the system to achieve high frequency operation without requiring small gap dimensions. The gate electrode provides a dynamic control mechanism that decouples the relationship between gap size and frequency, enabling frequency tuning while maintaining stable critical current characteristics.
3Adaptability or versatility
If graphene is used as the channel material, then the oscillation frequency can be tuned over a wide range, but the device requires cryogenic operation
Solution Approach 1:
The patent uses a composite material structure combining graphene channel with superconducting terminals (such as niobium or aluminum). This composite approach leverages the unique properties of graphene for frequency tuning while using superconducting materials to enable operation at cryogenic temperatures. The combination achieves wide frequency tuning range (24-100 GHz) while maintaining functionality at low temperatures required for superconductivity.
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
The system achieves tunable oscillation frequencies ranging from 24 GHz to 100 GHz, enabling its use in cryogenic computing and other applications by adjusting the gate voltage, while maintaining high electron mobility and low resistance.
Implementation Method 1
a first superconducting terminal, a second superconducting terminal, and a graphene channel together forming a Josephson junction having an oscillation frequency
Implementation Method 2
the conductive gate being configured, upon application of a voltage across the conductive gate and the graphene channel, to modify the oscillation frequency
Implementation Method 3
a refrigerator configured to cool the graphene sheet to a temperature below 4 K
Data Source
AI summary
A tunable oscillator including a Josephson junction. In some embodiments, the tunable oscillator includes a first superconducting terminal, a second superconducting terminal, a graphene channel including a portion of a graphene sheet, and a conductive gate. The first superconducting terminal, the second superconducting terminal, and the graphene channel together may form a Josephson junction having an oscillation frequency, and the conductive gate may be configured, upon application of a voltage across the conductive gate and the graphene channel, to modify the oscillation frequency.