Researchers have observed for the first time the existence of decoupled lattice and charge excitations in a new class of superconducting materials, the AV3Sb5 kagome compounds (where A can be K, Rb, or Cs). This discovery, made using inelastic neutron spectroscopy and inelastic X-ray scattering, sheds light on the complex interplay between crystal structure and electronic properties in these materials, which exhibit a charge density wave (CDW) phase and superconductivity.

Kagome materials, with their two-dimensional networks of intertwined triangles, are of great interest due to their topological and correlated properties. In AV3Sb5, the CDW phase is known to coexist or compete with superconductivity. Until now, it was assumed that lattice distortions associated with the CDW were intrinsically linked to charge density modulations. However, this study reveals that phononic excitations (lattice vibrations) and charge excitations can behave independently, even in the same energy and momentum region.

The experiments showed that, at temperatures below the transition to the CDW phase, anomalous phononic modes appear that do not directly couple to charge excitations. This dissociation suggests that the formation of the CDW in these materials is a more complex phenomenon than previously thought, possibly involving multiple degrees of freedom that interact in non-trivial ways. Understanding this decoupling is crucial for unraveling the mechanisms underlying superconductivity and topological phases in kagome materials, opening new avenues for the design of materials with controlled electronic properties.