Unveiling the nature of electronic transitions in RbV3Sb5 with avoided level crossing μSR

Layered kagome metals AV3⁢Sb5 provide a unique platform for studying the interplay between a variety of electronic orders, including superconductivity, charge density waves, nematic phases, and more. Understanding the evolution of the electronic state from the charge density wave to the superconducting transition is essential for unraveling the interplay of charge, spin, and lattice degrees of freedom giving rise to the unusual magnetic properties of these nonmagnetic metals. Previous zero-field and high-field muon spin relaxation (𝜇⁢SR) studies revealed two anomalies in the muon spin relaxation rate, a first change at 𝑇CDW∼100K and a second steep increase at 𝑇*∼40K, further enhanced by an applied magnetic field, thus suggesting a contribution of magnetic origin. In this Letter, we use the avoided level crossing 𝜇⁢SR technique to investigate charge order in near-zero applied field. By tracking the temperature dependence of quadrupolar level-crossing resonances, we examined the evolution of the electric field gradient at V nuclei in the kagome plane. Our results show a significant rearrangement of the charge density starting at 𝑇* indicating a transition in the charge distribution, likely electronic in origin, well below 𝑇CDW. These findings, combined with previous 𝜇⁢SR, scanning tunneling microscopy, and nuclear magnetic resonance (NMR) studies, emphasize the intertwined nature of proximate phases in these systems, with the charge rearrangement dominating the additional increase in 𝜇⁢SR relaxation rate below 𝑇*.