Abstract
Temperature-dependent reflectivity studies on the nonmagnetic kagome metal in a broad energy range (, equivalent to 6 meV–2.5 eV) down to 10 K are reported. Below 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 (100 meV) and (45 meV), the latter visible below 50 K only. Additionally, two modes at respectively (20 meV) and (53 meV) can be traced both above and below . They show strong anomalies already above with a further renormalization across the transition, suggesting the importance of the electron-phonon coupling in in both normal and CDW states. While the mode can be attributed to the phonon, the mode could not be reproduced in our phonon calculations. The antiresonance nature of this mode suggests a nontrivial electron-phonon coupling in . 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 .
5 More- Received 14 December 2021
- Revised 5 February 2022
- Accepted 2 June 2022
DOI:https://doi.org/10.1103/PhysRevB.105.245123
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