Weyl metal is regarded as a platform toward interacting topological states of matter, where its topological structure gives rise to anomalous transport phenomena, referred to as chiral magnetic effect and "negative" magneto-resistivity, the origin of which is chiral anomaly. Recently, the negative magneto-resistivity has been observed with the signature of weak anti-localization at x = 3 ∼ 4 % in Bi1−xSbx, where magnetic field is applied in parallel with electric field (E B). Based on the Boltzmann-equation approach, we find the negative magneto-resistivity in the presence of weak anti-localization. An essential ingredient is to introduce the topological structure of chiral anomaly into the Boltzmann-equation approach, resorting to semi-classical equations of motion with Berry curvature.
Ohm's law is a fundamental paradigm in the electrical transport of metals. Any transport signatures violating Ohm's law would give an indisputable fingerprint for a novel metallic state. Here, we uncover the breakdown of Ohm's law owing to a topological structure of the chiral anomaly in the Weyl metal phase. We observe nonlinear I-V characteristics in BiSb single crystals in the diffusive limit, which occurs only for a magnetic-field-aligned electric field (E∥B). The Boltzmann transport theory with the charge pumping effect reveals the topological-in-origin nonlinear conductivity, and it leads to a universal scaling function of the longitudinal magnetoconductivity, which completely describes our experimental results. As a hallmark of Weyl metals, the nonlinear conductivity provides a venue for nonlinear electronics, optical applications, and the development of a topological Fermi-liquid theory beyond the Landau Fermi-liquid theory.
Removal of H2S by a commercially available zinc oxide sorbent was studied using a packed-bed reactor for
desulfurizing the gas produced from steam-hydrogasification of carbonaceous materials. Experimental runs
were conducted to monitor sulfur removal efficiency and H2S breakthrough time for the operation variables
such as reaction temperature, steam content, space velocity, inlet H2S concentration, and sorbent particle
size. For the inlet gas with 45 vol % steam content, the initial sulfur removal efficiency exhibited a maximum
around 636 K. Varying the steam content of inlet gas affected the equilibrium of sorbent sulfidation in a
reversible way, leading to the decrease of sulfur capture capacity of the sorbent as the steam content increased.
Increasing the space velocity from 8 000 to 24000 h-1 decreased sulfur capture capacity significantly, indicating
the deterioration of gas−solid contact in the reactor at the increased gas flow rates. Inlet H2S concentration
was varied from 100 to 800 ppmv to reflect the diversity of steam-hydrogasifier feedstocks, which affected
sulfur capture capacity of the sorbent in such a way that the extent of sorbent utilization was limited by the
increased H2S concentration. Sorbent particle size was varied from 150−250 to 425−1000 μm to look into
the effect of intraparticle mass transfer limitation. The particles greater than 425 μm exhibited the sulfur
capture capacity that was limited by the reduced extent of sorbent utilization.
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