Low-energy optical properties of the nonmagnetic kagome metal CsV3Sb5

Temperature-dependent reflectivity measurements on the kagome metal CsV3Sb5 in a broad frequency range of 50-20 000 cm(-1) down to T=10 K are reported. The charge-density wave (CDW) formed below T-CDW = 94 K manifests itself in a prominent spectral-weight transfer from low to higher energy regions. The CDW gap of 60-75 meV is observed at the lowest temperature and shows significant deviations from an isotropic BCS-type mean-field behavior. Absorption peaks appear at frequencies as low as 200 cm(-1) and can be identified with interband transitions according to density-functional calculations. The change in the interband absorption compared to KV3Sb5 reflects the inversion of band saddle points between the K and Cs compounds. Additionally, a broader and strongly temperature-dependent absorption feature is observed below 1000 cm(-1) and assigned to a displaced Drude peak. It reflects localization effects on charge carriers.

Automated summary

Temperature-dependent reflectivity measurements were conducted on the kagome metal CsV3Sb5 in a wide frequency range, with notable spectral-weight transfer attributed to the charge-density wave (CDW) formed below 94 K. A CDW gap of 60-75 meV was observed at the lowest temperature, showing significant deviations from an isotropic BCS-type mean-field behavior. The interband absorption peaks, as low as 200 cm(-1), are associated with band transitions according to density-functional calculations, with differences observed between CsV3Sb5 and KV3Sb5 compounds. Additionally, a temperature-dependent absorption feature below 1000 cm(-1) was assigned to a displaced Drude peak, indicating localization effects on charge carriers.