New preprint: Switchable half-quantum flux states in a ring of the kagome superconductor CsV3Sb5
Our preprint Switchable half-quantum flux states in a ring of the kagome superconductor CsV3Sb5 was posted to arXiv on December 10, 2025. By turning high-quality kagome crystals into mesoscopic superconducting rings, the study establishes a phase-sensitive transport probe of unconventional superconductivity.
Why this matters
In a conventional superconducting ring, the Little-Parks effect is periodic in the standard superconducting flux quantum h/2e. A shift by half a flux quantum is a direct indication that the superconducting wave function accumulates an additional phase around the ring. Such measurements therefore provide information about pairing symmetry that cannot be obtained from the transition temperature alone.
Key findings
At low bias, the CsV3Sb5 rings show π-shifted Little-Parks oscillations, with the extrema displaced by half a superconducting flux quantum. The effect is highly reproducible: 12 of the 13 measured devices display the intrinsic π-shifted response. This device-to-device consistency is important for excluding accidental flux trapping or effects specific to a single device’s geometry.
A bias current reversibly switches the oscillations from the π-shifted state to the conventional state. In the intermediate regime, the oscillation period becomes h/4e. The continuous evolution between these regimes indicates competition and coexistence between distinct superconducting components, creating a controllable route to fractional-flux states in a solid-state device.
LinLab’s role
Dr. Ben-Chuan LIN supervised the project, conceived the study, and designed the experiments. Dr. Shuo WANG developed the etching process needed to fabricate the fragile thin-flake rings and produced all devices used in the main study. Dr. Lin and Dr. Wang performed the transport measurements. Dr. Wang, co-author Ze-Nan Wu, and Dr. Lin also carried out the supporting statistical experiments across multiple devices. This combination of microfabrication, low-noise transport, and reproducibility testing is a central strength of the work.
Collaboration and outlook
Professor Mark H. Fischer’s group at the University of Zurich and Professor Emeritus Manfred Sigrist’s group at ETH Zurich developed the theoretical framework for the competing superconducting components. The ability to switch flux states electrically suggests new ways to investigate multicomponent pairing and may ultimately inform superconducting circuits in which phase and flux are active, controllable degrees of freedom.