Speaker
Description
Kagome superconductors provide a rich platform to explore strong electronic correlations, superconductivity, pair density wave features and nontrivial band topology. Identifying a pairing symmetry is essential to understand the intertwined quantum phases. Despite numerous experimental efforts, focused on bulk crystals, there is no consensus for microscopic origin so far. Additionally, van der Waals flakes show distinct phases that are hard to probe with conventional methods due to the micron-size. We employ hybrid microwave circuits in which van der Waals kagome flakes are noninvasively coupled to superconducting resonators with preserved interface. This method enables microwave measurements with high coherence and low loss for the superconducting electrodynamic response at ultra-low temperatures. Using this technique, we resolve the temperature evolution of its superfluid response. A linear decrease in the temperature dependent resonance frequency is observed, inconsistent with a fully gapped state and instead indicative of nodal superconductivity. Our finding provides a crucial insight into the microscopic pairing mechanism in kagome superconductors, and establishes microwave resonators as a powerful probe of pairing symmetry in low-dimensional superconductors.