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Free keywords:
Condensed Matter, Superconductivity, cond-mat.supr-con, Condensed Matter, Mesoscale and Nanoscale Physics, cond-mat.mes-hall, Condensed Matter, Strongly Correlated Electrons, cond-mat.str-el,Quantum Physics, quant-ph
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$_\text{c}$. 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$_\text{c}$ = 20K. At the lowest fields and
close to T$_\text{c}$, 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.
