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arXiv · 1203.3176

Hybridization gap versus hidden order gap in URu$_2$Si$_2$ as revealed by optical spectroscopy

W. T. Guo·Z. G. Chen·T. J. Williams·J. D. Garrett·G. M. Luke·N. L. Wang
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Abstract

We present the in-plane optical reflectance measurement on single crystals of URu$_2$As$_2$. The study revealed a strong temperature-dependent spectral evolution. Above 50 K, the low frequency optical conductivity is rather flat without a clear Drude-like response, indicating a very short transport life time of the free carriers. Well below the coherence temperature, there appears an abrupt spectral weight suppression below 400 cm$^{-1}$, yielding evidence for the formation of a hybridization energy gap arising from the mixing of the conduction electron and narrow f-electron bands. A small part of the suppressed spectral weight was transferred to the low frequency side, leading to a narrow Drude component, while the majority of the suppressed spectral weight was transferred to the high frequency side centered near 4000 cm$^{-1}$. Below the hidden order temperature, another very prominent energy gap structure was observed, which leads to the removal of a large part of the Drude component and a sharp reduction of the carrier scattering rate. The study revealed that the hybridization gap and the hidden orger gap are distinctly different: they occur at different energy scales and exhibit completely different spectral characteristics.

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W. T. Guo, Z. G. Chen, T. J. Williams, J. D. Garrett, G. M. Luke, N. L. Wang. 2012-03-14. Hybridization gap versus hidden order gap in URu$_2$Si$_2$ as revealed by optical spectroscopy. https://doi.org/10.1103/physrevb.85.195105

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