Possible star-of-David pattern charge density wave with additional modulation in the kagome superconductor CsV3Sb5

Abstract

AV ₃Sb ₅ ( A = K, Rb, Cs) is a novel kagome superconductor coexisting with the charge density wave (CDW) order. Identifying the structure of the CDW order is crucial for understanding the exotic normal state and superconductivity in this system. Here, we report ⁵¹V nuclear magnetic resonance (NMR) and ^121/123Sb nuclear quadrupole resonance (NQR) studies on kagome-metal CsV ₃Sb ₅. Below the CDW transition temperature T _CDW ~ 98 K, an abrupt change of spectra was observed, indicating that the transition is of the first order. By further analyzing the spectra, we find that the CDW order is commensurate. And most remarkably, the obtained experimental results suggest that the charge modulation of the CDW order is of star-of-David pattern and accompanied by an additional charge modulation in bulk below T ^* ~ 40 K. Our results revealing the unconventional CDW order provide new insights into AV ₃Sb ₅.