Unusual paramagnetic phenomena in granular high-temperature superconductors—A consequence of d- wave pairing?

Manfred Sigrist; T. M. Rice

doi:10.1103/RevModPhys.67.503

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Unusual paramagnetic phenomena in granular high-temperature superconductors—A consequence of d- wave pairing?

Manfred Sigrist, T. M. Rice

DOI 10.1103/RevModPhys.67.503 · Reviews of Modern Physics

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Abstract

This colloquium reviews some unusual paramagnetic phenomena in granular high-temperature superconductors. These are consistently explained by assuming that there is frustration in the coupling patterns between the neighboring grains. Such frustration effects occur in a natural way in a multiply connected superconductor with Josephson junctions if the order parameter has unconventional symmetry due to Cooper pairing in a higher angular momentum channel, e.g., d- wave pairing. A simple model is introduced to describe the magnetic properties of a frustrated granular superconductor. Large orbital magnetic moments are spontaneously created, leading to superparamagnetic behavior. These results suggest that the unusual paramagnetic phenomena are a consequence of unconventional symmetry of the pairing state in the high-temperature superconductors.