Superconducting fluctuations observed far above T$_\mathrm{c}$ in the isotropic superconductor K$_3$C$_{60}$

Gregor Jotzu; Guido Meier; Alice Cantaluppi; Andrea Cavalleri; Daniele Pontiroli; Mauro Riccò; Arzhang Ardavan; Moon-Sun Nam

paper

Superconducting fluctuations observed far above T $_{c}$ in the isotropic superconductor K $_{3}$ C $_{60}$

arXiv:2109.08679

Abstract

Alkali-doped fullerides are strongly correlated organic superconductors that exhibit high transition temperatures, exceptionally large critical magnetic fields and a number of other unusual properties. The proximity to a Mott insulating phase is thought to be a crucial ingredient of the underlying physics, and may also affect precursors of superconductivity in the normal state above T $_{c}$ . We report on the observation of a sizeable magneto-thermoelectric (Nernst) effect in the normal state of K $_{3}$ C $_{60}$ , which displays the characteristics of superconducting fluctuations. The anomalous Nernst effect emerges from an ordinary quasiparticle background below a temperature of 80K, far above T $_{c}$ = 20K. At the lowest fields and close to T $_{c}$ , the scaling of the effect is captured by a model based on Gaussian fluctuations. The temperature up to which we observe fluctuations is exceptionally high for a three-dimensional isotropic system, where fluctuation effects are usually suppressed.

Superconducting fluctuations observed far above Tc​ in the isotropic superconductor K3​C60​

Abstract

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Superconducting fluctuations observed far above T $_{c}$ in the isotropic superconductor K $_{3}$ C $_{60}$