Flux-tunable transmon incorporating a van der Waals superconductor via an Al/AlOx/4Hb-TaS2 Josephson junction
2026-01-30 10:59
21 浏览
Incorporating van der Waals (vdW) superconductors into Josephson elements extends circuit-QED beyond conventional Al/AlO
unconventional condensates and subgap excitations. In this work, we realize a flux-tunable transmon whose nonlinear inductive element is an Al/AlO
The tunnel barrier is formed by sequential deposition and full in-situ oxidation of ultrathin Al layers on an exfoliated 4Hb-TaS
a robust, repeatable hybrid junction process compatible with standard transmon fabrication. Embedding the device in a three-dimensional copper cavity, we observe a SQUID-like
flux-dependent spectrum that is quantitatively reproduced by a standard dressed transmon--cavity Hamiltonian, from which we extract parameters in the transmon regime. Across
measured devices we obtain sub-microsecond energy relaxation (
also find a pronounced discrepancy between the Josephson energy inferred from spectroscopy and that expected from the Ambegaokar--Baratoff relation using room-temperature
junction resistances, pointing to nontrivial junction physics in the hybrid Al/AlO/4Hb-TaS system. Although we do not resolve material-specific subgap modes in the present geometry,
/4Hb-TaS system. Although we do not resolve material-specific subgap modes in the present geometry, this work establishes a practical route to integrating 4Hb-TaS into coherent quantum circuits and provides a baseline for future edge-sensitive designs aimed at enhancing coupling to
into coherent quantum circuits and provides a baseline for future edge-sensitive designs aimed at enhancing coupling to boundary and subgap degrees of freedom in vdW superconductors.
Link to the article is here.
