Speaker
Description
Kagome superconductors provide an ideal platform for investigating the interplay between non-trivial band topology, electronic correlations, lattice instabilities, and unconventional superconductivity [1,2]. Among them KV$_3$Sb$_5$ has attracted considerable interest owing to the coexistence of superconductivity and charge density wave (CDW) order [1-4], offering a unique opportunity to explore the microscopic origin of correlated electronic phases.
Here, we combine temperature-dependent X-ray absorption spectroscopy (XAS) with spatially resolved XAS ($\mu$XAS) and nano-focused angle-resolved photoemission spectroscopy (nanoARPES) to investigate the relationship between local distortions and electronic ordering in KV$_3$Sb$_5$. XAS measurements reveal clear signatures of local structural changes across the CDW transition [5]. In particular, the V-Sb bond distance exhibits an anomaly already above the CDW transition temperature (T$_{CDW}\sim$78 K), indicating the presence of precursor lattice distortions. XANES measurements further demonstrate that these structural modifications are accompanied by changes in the electronic states, providing evidence for CDW-related electronic fluctuations well above the onset of long-range order.
Complementary nanoARPES measurements directly visualize the spatial evolution of the electronic structure [6]. At low temperature, the material displays a percolative network of CDW domains with distinct spectral signatures, revealing intrinsic inhomogeneity. These textures disappear at room temperature, where a homogeneous electronic structure is recovered, consistent with the melting of CDW correlations. The combined results provide a unified picture in which local lattice distortions precede and promote the development of electronic ordering, highlighting the strong coupling between lattice and electronic degrees of freedom in the kagome superconductor KV$_3$Sb$_5$.
References:
[1] S. D. Wilson et al., Nature Reviews Materials 9, 420 (2024).
[2] M. Li at al., Chinese Physics B 34, 017101 (2025).
[3] K. Jiang et al., National Science Review 10, nwac199 (2023).
[4] X. Lai et al., Small Methods, 2402163 (2025).
[5] G. Tomassucci et al., Journal of Physics and Chemistry of Solids 211, 113449 (2026).
[6] G. Tomassucci et al., Journal of Physics: Condensed Matter (2026).