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Breakdown of Fermi-liquid theory in a cuprate superconductor

R. W. Hill·Cyril Proust·Louis Taillefer·P. Fournier·R. L. Greene
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Abstract

The behaviour of electrons in solids is remarkably well described by Landau's Fermi-liquid theory, which says that even though electrons in a metal interact they can still be treated as well-defined fermions, called ``quasiparticles''. At low temperature, the ability of quasiparticles to transport heat is strictly given by their ability to transport charge, via a universal relation known as the Wiedemann-Franz law, which no material in nature has been known to violate. High-temperature superconductors have long been thought to fall outside the realm of Fermi-liquid theory, as suggested by several anomalous properties, but this has yet to be shown conclusively. Here we report on the first experimental test of the Wiedemann-Franz law in a cuprate superconductor, (Pr,Ce)$_2$CuO$_4$. Our study reveals a clear departure from the universal law and provides compelling evidence for the breakdown of Fermi-liquid theory in high-temperature superconductors.

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R. W. Hill, Cyril Proust, Louis Taillefer, P. Fournier, R. L. Greene. 2001-12-14. Breakdown of Fermi-liquid theory in a cuprate superconductor. https://doi.org/10.1038/414711a

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