Superconducting fluctuations observed far above Tc in the isotropic superconductor K3C60

Journal article

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 sizable magneto-thermoelectric (Nernst) effect in the normal state of K₃C₆₀, which displays the characteristics of superconducting fluctuations. This nonquasiparticle Nernst effect emerges from an ordinary quasiparticle background below a temperature of 80 K, far above T_C = 20 K. At the lowest fields and close to T_C, the scaling of the effect is captured by a model based on Gaussian fluctuations. The behavior at higher magnetic fields displays a symmetry between the magnetic length and the correlation length of the system. The temperature up to which we observe fluctuations is exceptionally high for a three-dimensional isotropic system, where fluctuation effects are expected to be suppressed.

Authors: Jotzu, G; Meier, G; Cantaluppi, A; Cavalleri, A; Pontiroli, D

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Physical Society
• Journal: Physical Review X
• Volume: 13
• Issue: 2
• Article number: 021008
• Publication date: 2023-04-17
• Acceptance date: 2023-02-09
• DOI: 10.1103/PhysRevX.13.021008
• EISSN: 2160-3308
• Language: English
• Keywords: FFR