A method to access the electro-mechanical properties of superconducting thin film under uniaxial compression
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RESEARCH PAPER
A method to access the electro‑mechanical properties of superconducting thin film under uniaxial compression Xiyang Su1,2 · Cong Liu1,2 · Jun Zhou1,2 · Xingyi Zhang1,2 · Youhe Zhou1,2 Received: 1 May 2020 / Revised: 12 June 2020 / Accepted: 15 July 2020 © The Chinese Society of Theoretical and Applied Mechanics and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Superconducting thin films are widely used in superconducting quantum interferometers, microwave devices, etc. The electrical performance of a superconducting thin film is often affected by structural deformation or stress. Based on four-point bending of a Cu-Be beam, we constructed a device that could apply uniaxial, uniform, compressive strain to a superconducting thin film at both room temperature and the temperature of liquid nitrogen. The thin film was placed into a slot carved in the Cu-Be beam. We optimized the size of this slot via numerical simulation. Our results indicated that the slot width was optimal when it was same as the width of the Cu-Be beam. Notably, the sample bended hardly after machining two slits along width direction on both sides of the slot. A Y Ba2Cu3O7-δ-SrTiO3 (YBCO-STO) film was used as an example. It was loaded by the aforementioned device to determine its electrical characteristics as functions of the uniaxial-uniform-compressive strain. The optimized design allowed the sample to be compressed to a larger strain without breaking it. Keywords YBa2Cu3O7-δ thin film · Compressive strain · Critical current density
1 Introduction Superconducting films, which have many useful properties such as the Josephson effect [1], low surface resistance [2, 3], small size, and low weight, are widely used in superconducting quantum interferometers [4, 5], microwave devices [6–10], etc. The electrical performances of superconducting thin films are often affected by structural deformation or stress caused by temperature variation or electromagnetic force. This can be dangerous to the associated superconducting devices. Various instruments, such as grips, the U-spring, the Pacman, the Walters spring, and the Cu-Be beam [11–18], have been constructed to investigate the strain dependence of Jc and Tc in low- and high-temperature superconducting coated conductors and strands. Liu et al. [19], Wang et al. * Xingyi Zhang [email protected] 1
Department of Mechanics and Engineering Sciences, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou 730000, China
Key Laboratory of Mechanics on Disaster and Environment in Western China Attached to the Ministry of Education of China, Lanzhou University, Lanzhou 730000, China
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[20], and Zhang et al. [21] have recently developed instruments that measure the strain dependence of Jc in superconducting coated conductors. In addition, Yue et al. [22] have proposed a theory that fits well with the experimental results [23, 24]. The compressive strain dependence of Tc in YBa2Cu3O7-δ (YBCO) thin films was measured using a cantilevered beam [2
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