NMR study of charge density wave phase in the kagome metal RbV₃Sb₅

The mechanism of charge-density-wave (CDW) phase in one-dimensional lattices can be well described in theory. Whether similar mechanism works in two-dimensional systems is still a mystery. In this work, we employed ⁵¹V solid-state nuclear magnetic resonance (NMR) spectroscopy combined with first-principles computations to probe atomic structure and electronic properties at V sites in a quasi-two-dimensional crystal RbV₃Sb₅. Clear evidence of the CDW phase transition was observed from the temperature-dependent ⁵¹V NMR measurements. The sharp transition of ⁵¹V Knight shifts and electric field gradients (EFG) across the CDW transition supports the view that energy gap is formed by the nesting of partial Fermi surface in accompany with the superlattice formation. The calculated EFG parameters were also compared with our experiments, and the results suggest that the charge modulation of the CDW order is inverse Star-of-David pattern.