Optical study of RbV3Sb5: Multiple density-wave gaps and phonon anomalies

Temperature-dependent reflectivity studies on the nonmagnetic kagome metal RbV3Sb5 in a broad energy range (50???20000 cm???1, equivalent to 6 meV???2.5 eV) down to 10 K are reported. Below TCDW = 102 K, the optical spectra demonstrate a prominent spectral-weight transfer from low to higher energies as the fingerprint of the charge-density-wave (CDW) formation with the opening of a partial gap. A detailed analysis reveals two energy scales of respectively ???800 cm???1 (100 meV) and 360 cm???1 (45 meV), the latter visible below 50 K only. Additionally, two modes at respectively 160 cm???1 (20 meV) and 430 cm???1 (53 meV) can be traced both above and below TCDW. They show strong anomalies already above TCDW with a further renormalization across the transition, suggesting the importance of the electron-phonon coupling in RbV3Sb5 in both normal and CDW states. While the 160 cm???1 mode can be attributed to the E1u phonon, the 430 cm???1 mode could not be reproduced in our phonon calculations. The antiresonance nature of this mode suggests a nontrivial electron-phonon coupling in RbV3Sb5. A distinct localization peak observed at all temperatures signals damped electron dynamics, whereas the reduced Drude spectral weight manifests moderate deviations from the band picture in RbV3Sb5.

Automated summary

Temperature-dependent reflectivity studies have been conducted on the nonmagnetic kagome metal RbV3Sb5, revealing the spectral characteristics in a broad energy range. The observations indicate the formation of charge-density wave and the significance of electron-phonon coupling.