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

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.

5 pages

References in corpus (4)

• Imaging the Fano Lattice to 'Hidden Order' Transition in URu2Si2
• Gapped itinerant spin excitations account for missing entropy in the hidden order state of URu${}_2$Si${}_2$
• Interplay between SDW and induced local moments in URu2Si2
• Spin and orbital hybridization at specifically nested Fermi surfaces in URu${}_2$Si${}_2$

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• High-magnetic field lattice length changes in URu2Si2
• Optical conductivity of URu${}_2$Si${}_2$ in the Kondo Liquid and Hidden-Order Phases
• Detailed optical spectroscopy of the hybridization gap and the hidden order transition in high quality URu${}_2$Si${}_2$ single crystals
• Electrodynamics of the antiferromagnetic phase in URu${}_2$Si${}_2$
• Optical study of hybridization and hidden order in URu${}_2$Si${}_2$
• Anisotropic Kondo pseudo-gap in URu2Si2
• Quasiparticle Relaxation Dynamics in URu${}_{2-x}$Fe${}_x$Si${}_2$ Single Crystals