Fulleride superconductivity tuned by elastic strain due to cation compositional disorder

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

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.

• Language: English
• Keywords: fullerides
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FMF - Faculty of Mathematics and Physics
• Publication status: Published
• Publication version: Version of Record
• Year: 2024
• Number of pages: Str. 16485-19493
• Numbering: Vol. 15, iss. 40
• PID: 20.500.12556/RUL-164412
• UDC: 53
• ISSN on article: 2041-6539
• DOI: 10.1039/d4sc03399j
• COBISS.SI-ID: 212103427
• Publication date in RUL: 24.10.2024

Record is a part of a journal

• Title: Chemical science
• Shortened title: Chem. sci.
• Publisher: Royal Society of Chemistry
• ISSN: 2041-6539
• COBISS.SI-ID: 519832601

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• License: CC BY-NC 3.0, Creative Commons Attribution-NonCommercial 3.0 Unported
• Link: http://creativecommons.org/licenses/by-nc/3.0/
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Projects

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: P1-0125-2022
• Name: Fizika kvantnih in funkcionalnih materialov

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: J1-3007-2021
• Name: Kvantno procesiranje fulerenskih kubitov z diamantnimi senzorji