Work

Fulleride superconductivity tuned by elastic strain due to cation compositional disorder

Year: 2024

Type: article

Abstract: Dynamical fluctuations of the elastic strain in strongly correlated systems are known to affect the onset of metal-to-insulator or superconducting transitions. Here we report their effect on the properties of a family of bandwidth-controlled alkali-intercalated fullerene superconductors. We introduce elastic strain through static local structural disorder in a systematic and controllable way in the fcc-structured K$_x$Cs$_{3-x}$C$_{60}$ (with potassium content, 0.22 $leq$ x$_K$ $leq$ 2) series of compositions by utilizing the difference in size between the K$^+$ and Cs$^+$ co-dopants. The occurrence of the crossover from the Mott–Jahn–Teller insulating (MJTI) state into the strongly correlated Jahn–Teller metal (JTM) on cooling is evidenced for the compositions with x$_K$ < 1.28 by both synchrotron X-ray powder diffraction (SXRPD) – anomalous reduction of the unit cell volume – and $^{133}$Cs NMR spectroscopy – sudden suppression in the $^{133}$Cs spin-lattice relaxation rates. The emerging superconducting state with a maximum critical temperature, T$_c$ = 30.9 K shows a characteristic dome-like dependence on the unit-cell volume or equivalently, on the ratio between the on-site Coulomb repulsion, U, and the bandwidth, W. However, compared to the parent Cs$_3$C$_{60}$ composition in which cation disorder effects are completely absent, the maximum T$_c$ is lower by ∼12%. The reduction in T$_c$ displays a linear dependence on the variance of the tetrahedral-site cation size, $sigma_T^2$, thus establishing a clear link between structural-disorder–induced attenuation of critical elastic strain fluctuations and the electronic ground state.

Source: Repository of the University of Ljubljana (University of Ljubljana)

Authors: Okur, Esma H., Colman, Ross, Takabayashi, Yasuhiro, Jeglič, Peter, Ohishi, Yasuo, Kato, Kenichi, Arčon, Denis, Kubota, Yoshiki, Prassides, Kosmas

Institutions: Charles University, Nagoya Institute of Technology, Jožef Stefan Institute, Jožef Stefan International Postgraduate School, SPring-8, University of Ljubljana, Osaka Metropolitan University, Kyoto University of Advanced Science

Language: English

Topic: Fullerene Chemistry and Applications

Subfield: Organic Chemistry

Field: Chemistry

Domain: Physical Sciences

Open Access status: green

OpenAlex ID: W7047470446

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