Abstract
Non-Fermi-liquid (NFL), a significant deviation from Fermi-liquid theory, usually emerges near an order-disorder phase transition at absolute zero. Recently, a diverging susceptibility ...toward zero temperature was observed in a quasicrystal (QC). Since an electronic long-range ordering is normally absent in QCs, this anomalous behaviour should be a new type of NFL. Here we study high-resolution partial-fluorescence-yield x-ray absorption spectroscopy on Yb-based intermediate-valence icosahedral QCs and cubic approximant crystals (ACs), some of which are new materials, to unveil the mechanism of the NFL. We find that for both forms of QCs and ACs, there is a critical lattice parameter where Yb-valence and magnetism concomitantly exhibit singularities, suggesting a critical-valence-fluctuation-induced NFL. The present result provides an intriguing structure–property relationship of matter; size of a Tsai-type cluster (that is a common local structure to both forms) tunes the NFL whereas translational symmetry (that is present in ACs but absent in QCs) determines the nature of the NFL against the external/chemical pressure.
The Ag–In–Ce alloy is an approximant crystal to a Tsai-type quasicrystal and exhibits heavy-fermion (Kondo) physics. This new type of Kondo material exhibits spin-glass ordering below the freezing ...temperature Tf ∼ 0.3 K at ambient pressure. Here we investigated the effect of hydrostatic pressure on the Ag–In–Ce alloy. Spin-glass features, such as the frequency-dependent cusp near Tf in the ac magnetic susceptibility curve, were observed even under external pressure. In addition, the C/T value (where C is the specific heat) increased with decreasing temperature and exhibited a broad peak above Tf. The Tf increased as the pressure increased up to its highest value in the experiment (approximately 2.6 GPa).
Broadband tunability is a central theme in contemporary nanophotonics and metamaterials research. Combining metamaterials with phase change media offers a promising approach to achieve such ...tunability, which requires a comprehensive investigation of the electromagnetic responses of novel materials at subwavelength scales. In this work, we demonstrate an innovative way to tailor band-selective electromagnetic responses at the surface of a heavy fermion compound, samarium sulfide (SmS). By utilizing the intrinsic, pressure sensitive, and multi-band electron responses of SmS, we create a proof-of-principle heavy fermion metamaterial, which is fabricated and characterized using scanning near-field microscopes with <50 nm spatial resolution. The optical responses at the infrared and visible frequency ranges can be selectively and separately tuned via modifying the occupation of the 4f and 5d band electrons. The unique pressure, doping, and temperature tunability demonstrated represents a paradigm shift for nanoscale metamaterial and metasurface design.
We report ultrafast electronic relaxation dynamics of yttrium-doped samarium monosulfide, Sm0.83Y0.17S, which is one of valence fluctuating compounds, by pump-probe measurements. We observed a large ...increase of the Drude weight in the reflectivity spectrum by the photo-excitation and a double exponential decay of the relaxation time to a metastable state. This suggests that the photo-induced effect can be explained as the change of carrier density. The metastable state has a long lifetime ( > 1 ns) and the carrier density is slightly higher than that before the photo-excitation.
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