On-Chip Tuning of Superconductivity in Fullerides via Current-Driven Rb<sup>+</sup> Intercalation.

Shchukin, Konstantin P; Gallego Lacey, Oliver N; Coquinot, Baptiste; Jakowski, Jacek; Huang, Jingsong; Staudenmayer, Patrik; Falke, Yannic; Pandeya, Ram Prakash et al. · ACS Nano · 2026

basic_science · Level V

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Abstract

An in-operando electro-intercalation method for the on-chip synthesis of alkali-metal-intercalated materials and their Raman spectroscopic and transport characterization in ultrahigh vacuum (UHV) is developed. We apply this method to synthesize fulleride superconductors via Rb<sup>+</sup> intercalation into a C<sub>60</sub> film. During the intercalation, we monitor the stoichiometry via UHV-Raman spectroscopy and probe superconductivity via transport measurements. An increase of the superconducting transition temperature from 7.0 K to 14.5 K is observed when the stoichiometry is tuned from Rb<sub>2.7</sub>C<sub>60</sub> to Rb<sub>3</sub>C<sub>60</sub>. In our experiment, an ionic Rb<sup>+</sup> flux into the host material is induced by an applied electronic current via a Butler-Volmer-type mechanism. Electro-intercalation captivates through improved stoichiometric precision, the ability to smoothly vary stoichiometry via duration of current application, and the absence of a lower limit of the volume of the host material. It represents a powerful concept for the on-chip synthesis of intercalated materials, battery research, and beyond.