Glass-like Cross-plane Thermal Conductivity of Kagome Metals RbV3Sb5 and CsV3Sb5

doi:10.21203/rs.3.rs-2949992/v1

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Glass-like Cross-plane Thermal Conductivity of Kagome Metals RbV₃Sb₅ and CsV₃Sb₅

https://doi.org/10.21203/rs.3.rs-2949992/v1

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This work reports the thermal conductivity of RbV₃Sb₅ and CsV₃Sb₅ with three-dimensional charge density wave phase transitions from 80 K to 400 K measured by pump-probe thermoreflectance techniques. At room temperature, the in-plane (basal plane) thermal conductivities are found moderate, i.e., 12 W m^-1 K^-1 of RbV₃Sb₅ and 8.8 W m^-1 K^-1 of CsV₃Sb₅,and ultralow cross-plane (stacking direction) thermal conductivities are observed, with 0.72 W m^-1 K^-1 of RbV₃Sb₅ and 0.49 W m^-1 K^-1 of CsV₃Sb₅ at 300 K. A unique glass-like temperature dependence in the cross-plane thermal conductivity is discovered, which decreases monotonically even lower than the Cahill-Pohl limit as the temperature decreases below the phase transition point T_CDW. This temperature dependence is found to obey the hopping transport picture. In addition, a peak in cross-plane thermal conductivity is observed at T_CDW as a fingerprint of the modulated structural distortion along the stacking direction.