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arXiv · 1811.01026

Perfect separation of intraband and interband excitations in PdCoO$_2$

C. C. Homes·S. Khim·A. P. Mackenzie
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Abstract

The temperature dependence of the optical properties of the delafossite PdCoO$_2$ has been measured in the a-b planes over a wide frequency range. The optical conductivity due to the free-carrier (intraband) response falls well below the interband transitions, allowing the plasma frequency to be determined from the $f$-sum rule. Drude-Lorentz fits to the complex optical conductivity yield estimates for the free-carrier plasma frequency and scattering rate. The in-plane plasma frequency has also been calculated using density functional theory. The experimentally-determined and calculated values for the plasma frequencies are all in good agreement; however, at low temperature the optically-determined scattering rate is much larger than the estimate for the transport scattering rate, indicating a strong frequency-dependent renormalization of the optical scattering rate. In addition to the expected in-plane infrared-active modes, two very strong features are observed that are attributed to the coupling of the in-plane carriers to the out-of-plane longitudinal optic modes.

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C. C. Homes, S. Khim, A. P. Mackenzie. 2019-05-06. Perfect separation of intraband and interband excitations in PdCoO$_2$. https://doi.org/10.1103/physrevb.99.195127

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