Flat bands once considered inactive are now shaping quantum behaviour in a superconducting material called kagome due to its unique atomic structure.
Flat electronic bands are quantum states where electrons have zero velocity, and are now confirmed to actively influence superconductivity and magnetism in kagome-lattice metal. These bands, enhances quantum correlation effects, changing CsCr₃Sb₅, into superconducting under pressure.
The study, published in Nature Communications, provides experimental validation for theories linking lattice geometry to emergent quantum phases. Unlike in most materials, where flat bands remain inert, here they operate within the active energy range and contribute to the system’s electronic and magnetic properties.
The kagome structure is a two-dimensional network of corner-sharing triangles. In CsCr₃Sb₅, this configuration hosts standing-wave electronic states. The research team used angle-resolved photoemission spectroscopy (ARPES) and resonant inelastic X-ray scattering (RIXS) to observe these features and measure their influence on quantum excitations.
Theoretical modelling based on a custom kagome lattice confirmed the signatures seen in the experiments. To achieve these measurements, the team synthesised ultra-pure crystals of CsCr₃Sb₅, more than 100 times larger than in prior studies.
The work was conducted by Rice University in collaboration with Taiwan’s National Synchrotron Radiation Research Center. It draws a direct link between flat-band physics and controllable quantum behaviour in solid-state systems.
The findings suggest a route to designing materials where quantum states—such as superconductivity, magnetism, or topological effects—can be tuned through structural and chemical controls.
