We report an optical spectroscopy study of a single-crystal sample of PrSb, one of the monoantimonide $R\mathrm{Sb}$ compounds, which show interesting properties, such as topological nontrivial surface states and extremely large magnetoresistance. The plasma frequency is revealed at about $4300\phantom{\rule{0.28em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$, suggesting a low carrier density. In addition, we found two quasilinear components with variable slopes in the real part of the optical conductivity ${\ensuremath{\sigma}}_{1}(\ensuremath{\omega})$. In combination with theoretical calculations which reveal a band inversion, our results may provide optical spectroscopic evidence of a topological nontrivial property in PrSb.
We report magnetic susceptibility, resistivity and optical spectroscopy study on single crystal sample DySb. It exhibits extremely large magnetoresistance (XMR), and a magnetic phase transition from paramagnetic (PM) to antiferromagnetic (AFM) state at about 10 K. A 'screened' plasma edge at about 4000 cm-1 is revealed by optical measurement, which suggests that the material has a low carrier density. With decreasing temperature, the 'screened' plasma edge shows a blue shift, possibly due to a decrease of the effective mass of carriers. Notably, an anomalous temperature dependent midinfrared absorption feature is observed in the vicinity of the 'screened' plasma edge. In addition, it can be connected to the inflection point in the real part of the dielectric function [Formula: see text], the frequency of which exactly tracks the temperature dependent 'screened' plasma frequency. This phenomena can be explained by the appearance of a coupled electron-plasmon 'plasmaron' feature.
We report resistivity, specific heat and optical spectroscopy measurements on single crystal samples of [Formula: see text] [Formula: see text] [Formula: see text] and [Formula: see text] [Formula: see text] [Formula: see text]. We observed clear temperature-induced spectral weight suppression below 4000 [Formula: see text] for both compounds in the conductivity spectra [Formula: see text], indicating the progressive formation of gap-like features with decreasing temperature. The suppressed spectral weight transfers mostly to the higher energy region. This observation reflects the presence of the correlation effect in the compounds. We attribute the correlation effect to the Co 3d electrons.
We report resistivity, specific heat and optical spectroscopy measurements on single crystal samples of La$_3$Co$_4$Sn$_{13}$ and Ce$_3$Co$_4$Sn$_{13}$. We observed clear temperature-induced spectral weight suppression below 4000 \cm for both compounds in conductivity spectra $\sigma_1(\omega)$, indicating the progressive formation of gap-like features with decreasing temperature. The suppressed spectral weight transfers mostly to the higher energy region. The observation reflects the presence of correlation effect in the compounds. We attribute the correlation effect to the Co 3d electrons.
Summary Methane migration in shale is affected by preadsorbed water. To understand this effect, we examined several key parameters, including the effective pore diameter Le, the pore volume distribution of Le, the effective porosity ϕe, the equivalent particle diameter da, and the water film thickness h. Using these parameters, we established an equivalent relationship linking the particle packing da and the Le and the ϕe of the capillary pores within a unit-length cuboid of particles. Based on this relationship, a conceptual model was developed to simulate methane adsorption and transport in partially saturated crushed shale, incorporating parameter estimation for the tangential momentum adjustment factor δ and methane desorption rate coefficient kd, where δ characterizes the slip flow intensity and kd is related to the Langmuir adsorption constant. The finite element method was used to calculate the methane permeability ke, Knudsen diffusion coefficient Dke, surface diffusion coefficient Ds, and adsorption phase transition rate Rm, which are all affected by adsorbed water. The model’s numerical results were validated through comparison with the results from adsorption experiments. These results revealed three distinct regions in the trend of the variation in δ with Le: a rapid increase in Region I (Le < 10 nm), a slowing increase in Region II (10 ≤ Le ≤ 100 nm), and a gradual increase in Region III (Le > 100 nm). In addition, kd is positively correlated with da. kd is also correlated with water saturation S; specifically, kd decreases when S ≤ 12%, increases when S = 12% to 45.8%, and decreases again when S exceeds 45.8%. The results also reveal overall negative correlations between h and ke, Dke, Ds and Rm. Furthermore, the rates of change in ke, Dke, Ds and Rm with increasing ε (ε is the bending coefficient associated with adsorbed water) range from 7.5% to 49.4%. Similarly, ke, Dke, and Ds increase by factors of 0.73–7.19 with increasing χ (χ is the coverage rate of the adsorbed water film). Additionally, as the adsorption time t increases, Ds initially increases rapidly, followed by a gradual increase. Between t = 500 seconds and 1,500 seconds, the rate of change in Ds decreases by 20%. Rm shows a three-stage relationship with t, namely, a rapid decrease from t = 0 seconds to 500 seconds, a steady decrease from 500 seconds to 1,000 seconds, and a stabilization from 1,000 seconds to 1,500 seconds, with Rm ranging from 1.10×10-11 mol/(m3·s) to 9.45×10-11 mol/(m3·s) overall. Ds increases with the adsorption amount ratio Ed (Ed is the ratio of the adsorption amount at t to the equilibrium adsorption amount). As Ed ranges from 0.2 to 0.6, the rate of change in Ds increases by 87% to 100%. Furthermore, Rm is negatively linearly correlated with Ed.
We report resistivity, magnetization, and optical spectroscopy study on single-crystal sample of ${\mathrm{Sr}}_{3}{({\mathrm{Ru}}_{0.985}{\mathrm{Fe}}_{0.015})}_{2}{\mathrm{O}}_{7}$. An upturn is observed in resistivity at about 30 K. Below 30 K, the dip in resistivity $R(\ensuremath{\omega}$), the suppression in scattering rate $1/\ensuremath{\tau}(\ensuremath{\omega})$, the peaklike feature in optical conductivity ${\ensuremath{\sigma}}_{1}(\ensuremath{\omega})$, and the remainder of spectral weight all suggest the formation of a pseudogap. In addition, one phonon peak at about $600\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ is distinguished at all temperatures, which has asymmetric line shape. Such asymmetric line shape can be fit by a Fano function, and the resulting Fano factor $1/{q}^{2}$ and linewidth $\ensuremath{\gamma}$ show significant increases below 30 K, giving further evidence for the formation of a pseudogap, which might originate from the partial $k$-space gap opening due to density wave instability.
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