Experimental investigation of the kinetic inductance in YBa2Cu3O7 square washer superconducting quantum interference devices

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Abstract
The inductance Ls of YBa2Cu3O7 thin‐film square washer dc superconducting quantum interference devices was measured directly from 4.2 K up to the critical temperature Tc of the film. Ls(T) diverges close to Tc. Examining the temperature dependence of Ls two contributions are distinguished: the magnetic inductance, defined by the outer device geometry, and the temperature‐dependent kinetic inductance Lk associated with the thin‐film slit structure. Lk is found to scale with the square of the magnetic penetration depth λ(T) in a broad temperature range. The specific magnetic inductance per unit length of a long slit within the washer is measured to be ∼0.3 pH/μm. The impact of Ls(T) on device performance at elevated temperature is discussed.