Experimental determination of the superconducting pairing state in YBCO from the phase coherence of YBCO-Pb dc SQUIDs

D. A. Wollman; D. J. Van Harlingen; W. C. Lee; D. M. Ginsberg; A. J. Leggett

doi:10.1103/PhysRevLett.71.2134

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Experimental determination of the superconducting pairing state in YBCO from the phase coherence of YBCO-Pb dc SQUIDs

D. A. Wollman, D. J. Van Harlingen, W. C. Lee, D. M. Ginsberg, and A. J. Leggett

Phys. Rev. Lett. 71, 2134 – Published 27 September 1993

An article within the collection: Heating up of Superconductors

Abstract

We present an experiment designed to determine directly the symmetry of the pairing state in the cuprate superconductors. From the magnetic flux modulation of YBCO-Pb dc SQUIDs, we determine the spatial anisotropy of the phase of the order parameter in single crystals of YBCO. The experimental results are complicated by SQUID asymmetries and the trapping of magnetic vortices, but taken as a whole give rather strong evidence for a phase shift of π that is predicted for the $d_{x}^{2 -}$ $y^{2}$ pairing state. This is further corroborated by single junction modulation measurements.

Received 18 June 1993

DOI:https://doi.org/10.1103/PhysRevLett.71.2134

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Heating up of Superconductors

This collection marks the 30th anniversary of the discovery of high-temperature superconductors. The papers selected highlight some of the advances that have been made to date, both in understanding why these compounds behave in the way they do, and in utilizing them in applications.