Calculation of Tc in a Normal-Superconductor Bilayer Using the Microscopic-Based Usadel Theory

Published

December 31, 2000

Author(s)

John M. Martinis, Gene C. Hilton, Kent D. Irwin, David A. Wollman

Abstract

The Usadel equations give a theory of superconductivity, valid in the diffusive limit, that is a generalization of the microscopic equations of the BCS theory. Because the theory is expressed in a tractable and physical form, even experimentalists can analytically and numerically calculate detailed properties of superconductors in physically relevant geometries. Here, we describe the Usadel equations and review their solution in the case of predicting the transition temperature T_c of a thin normal-superconductor bilayer. We also extend this calculation for thicker bilayers to show the dependence on the resistivity of the films. These results, which show a dependence on both the interface resistance and heat capacity of the films, provide important guidance on fabricating bilayers with reproducible transition temperatures.

Citation

Nuclear Instruments & Methods in Physics Research Section A-Accelerators Spectrometers Detectors and Associated Equipment

Volume

444

Issue

2000

Pub Type

Journals

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Keywords

microcalorimeter superconducting bilayer, transition edge sensor, Usadel

Citation

Martinis, J. , Hilton, G. , Irwin, K. and Wollman, D. (2000), Calculation of Tc in a Normal-Superconductor Bilayer Using the Microscopic-Based Usadel Theory, Nuclear Instruments & Methods in Physics Research Section A-Accelerators Spectrometers Detectors and Associated Equipment, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=27928 (Accessed October 9, 2025)