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تسجيل مستخدم جديدLow-energy optical properties of the non-magnetic kagome metal CsV$_3$Sb$_5$
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Temperature-dependent reflectivity measurements on the kagome metal CsV$_3$Sb$_5$ in a broad frequency range of $50-20000$ cm$^{-1}$ down to $T$=10 K are reported. The charge-density wave (CDW) formed below $T_{rm CDW}$ = 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 KV$_3$Sb$_5$ 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.
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The recently discovered kagome metal series $A$V$_3$Sb$_5$ ($A$=K, Rb, Cs) exhibits topologically nontrivial band structures, chiral charge order and superconductivity, presenting a unique platform for realizing exotic electronic states. The nature o
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Optical spectroscopy and density-functional calculations reveal electronic properties of the nonmagnetickagome metal KV$_3$Sb$_5$. Temperature and frequency-dependent optical measurements down to 10K and up to 2 eV energy range confirm bulk nature of
the charge-density-wave (CDW) state below 78 K and gauge the charge gap of $Delta_{CDW} approx$ 60 meV at 10 K. We further detect strong phonon anomalies and the prominent low-energy localization peak indicative of the unconventional charge transport caused by electron-phonon or electron-electron interactions. Possible CDW structures of KV$_3$Sb$_5$, the star and hexagon (inverse star), are strongly reminiscent of $p$-wave states expected in the Hubbard model on the kagome lattice at the filling level of the van Hove singularity. The proximity to this regime may have intriguing and far-reaching implications for the physics of KV$_3$Sb$_5$ and related materials.
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