Optical response of YbS and YbO at high pressures and the pressure-volume relation of YbS

Pressure induced valence transitions inf-electron systems

“…for YbS indicate anomalous behaviour around 100 kbar which could be associated with intermediate valence 76 . In particular, for this system a trivalent state cannot seemingly be realized.…”

Infrared and Terahertz Spectroscopy of Strongly Correlated Electron Systems under Extreme Conditions

“…Its energy gap is about 1.3 eV, and is located between a fully occupied 4f state and an unoccupied, mainly Yb 5d-derived conduction (c) band. An optical reflectance study of YbS using DAC was performed in 1980s by Syassen et al, without using IR-SR. 119) A peak in ð!Þ due to light absorption across the energy gap, namely, a gap excitation peak, was observed to shift to a lower energy with increasing pressure. The peak shift was extrapolated to zero energy at about 10 GPa, implying a gap closure near 10 GPa.…”

“…10 GPa. 119) Assuming that the increase in the mean Yb valence from 2 is equal to the density of c electrons, the analysis of spectral weight for the Drude peak indicated that the effective mass of c electrons is about 12 m à at 20 GPa. Namely, carriers in the metallic phase are moderately heavy.…”

“…For example, in the early 1980s, Syassen and Sonnenschein developed a high-pressure optical spectroscopy apparatus that covered the near IR to UV ranges (0.5-4 eV). 127) Syassen and coworkers studied various materials under high pressure such as K (potassium), 128) EuO, 129) YbS and YbO, 119) and Si. 92) At present, commercially available FTIR instruments coupled with a microscope (micro-FTIRs) generally cover a wide spectral range with a high spatial resolution and a high signal-to-noise ratio.…”

Pressure-Driven Topological Phase Transition in the Yb Chalcogenides YbO and YbS

“…In particular, for the chalcogenides of Eu, Sm, and Yb, 25 a fluctuating valence state is accessible under ambient or high pressure. [26][27][28][29][30][31] These rare-earth compounds providing a high probability of finding more TKIs, although there are few TKIs predicted in rare-earth pnictides and chalcogenides with a rock-salt structure at present. 32 In this work, we employ first-principles calculation based on the density functional theory (DFT) with the modified Becke-Johnson local density approximation plus Hubbard U (MBJLDA+U) to study the band topology of the Yb monochalcogenides YbO and YbS with a rock-salt structure (shown in Fig.…”