Topological quantum transition driven by charge-phonon coupling in higher-order topological insulators

We investigate a second-order topological quantum transition of a modified Kane-Mele model driven by electron-phonon interaction. The results show that the system parameters of the bare modified Kane-Mele model are renormalized by the electron-phonon interaction. Starting from the second-order topological phase for the bare model, the increasing electron-phonon coupling strength can drive the second-order topological insulator into a semimetal phase. Such a secondorder topological phase transition is characterized by the band-gap closing, discontinuity of averaged ferminoic number and topological invariant.Comment: 8 pages,6 figure

Effects of Disorder On Thouless Pumping In Higher-Order Topological Insulators

We investigate the effects of random onsite disorder on higher-order Thouless pumping of noninteracting fermionic Benalcazar-Bernevig-Hughes (BBH) model. The interplay of disorderinduced topological phase transition and delocalization-localization transition is extensively explored. The higher-order Thouless pumping is characterized by the quantized corner-to-corner charge transport and nonzero Chern number, and the delocalization-localization transition is analyzed by utilizing both inverse participation ratio and energy-level statistics. The results show that the quantized corner-to-corner charge transport is broken in the strong disorder, where the instantaneous bulk energy gap is closed due to effects of disorder. While, although the instantaneous eigenstates are localized, the charge transport remains quantized. This is attributed to delocalized Floquet states caused by the periodic driving. Furthermore, the phase transition from the quantized charge transport to topologically trivial pumping is accompanied by the disorder-induced delocalization-localization transition of Floquet states.Comment: 8 pages, 7figure

Bi2O2Se nanowires presenting high mobility and strong spin-orbit coupling

Systematic electrical transport characterizations were performed on high-quality Bi2O2Se nanowires to illustrate its great transport properties and further application potentials in spintronics. Bi2O2Se nanowires synthesized by chemical vapor deposition method presented a high field-effect mobility up to 1.34*104 cm2V-1s-1, and exhibited ballistic transport in the low back-gate voltage (Vg) regime where conductance plateaus were observed. When further increasing the electron density by increasing Vg, we entered the phase coherent regime and weak antilocalization (WAL) was observed. The spin relaxation length extracted from the WAL was found to be gate tunable, ranging from ~100 nm to ~250 nm and reaching a stronger spin-obit coupling (SOC) than the two-dimensional counterpart (flakes). We attribute the strong SOC and the gate tunability to the presence of a surface accumulation layer which induces a strong inversion asymmetry on the surface. Such scenario was supported by the observation of two Shubnikov-de Haas oscillation frequencies that correspond to two types of carriers, one on the surface, and the other in the bulk. The high-quality Bi2O2Se nanowires with a high mobility and a strong SOC can act as a very prospective material in future spintronics.Comment: 22 pages, 7 figure

Pavement dynamic monitoring data processing based on wavelet decomposition and reconfiguration methods

Early damage to asphalt pavements generally occurs due to the increasing traffic flow and the loads of vehicles, coupled with alternating high- and low-temperature cycles, freeze–thaw cycles, ultraviolet radiation, and other harsh environments. Several types of distress, such as rutting, cracking, and other damage, deteriorate the serviceability of asphalt pavements and shorten the road service life. Thus, the long-term structural mechanical response of asphalt pavements under the influence of loads and the environment is crucial data for the road sector, which provides guidance about road maintenance. Effectively processing the pavement dynamic monitoring data is a prerequisite to obtain the dynamic response of asphalt pavement structures. However, the dynamic monitoring data of pavements are often characterized by transient weak signals with strong noises, making it challenging to extract their essential characteristics. In this study, wavelet decomposition and reconstruction methods were applied to reduce the noise of pavement dynamic response data. The parameters of the signal-to-noise ratio (SNR) and root mean square error (RMSE) were introduced to compare and analyze the effect of the decomposition of two different wavelet functions: the symlet (sym) wavelet function and the Daubechies (db) wavelet function. The results showed that both the sym and db wavelet functions can effectively obtain the average similarity information and the detailed information of the dynamic response signals of the pavement, the SNR after the sym wavelet fixed-threshold denoising process is relatively higher, and the RMSE is smaller than that of the db wavelet. Thus, wavelet transformation exhibits good localization properties in both the time and frequency domains for processing pavement dynamic monitoring data, making it a suitable approach for handling massive pavement dynamic monitoring data

In Situ Wet Etching of MoS2@dWO3 Heterostructure as Ultra-Stable Highly Active Electrocatalyst for Hydrogen Evolution Reaction

Electrocatalysts featuring robust structure, excellent catalytic activity and strong stability are highly desirable, but challenging. The rapid development of two-dimensional transition metal chalcogenide (such as WO3, MoS2 and WS2) nanostructures offers a hopeful strategy to increase the active edge sites and expedite the efficiency of electronic transport for hydrogen evolution reaction. Herein, we report a distinctive strategy to construct two-dimensional MoS2@dWO3 heterostructure nanosheets by in situ wet etching. Synthesized oxygen-incorporated MoS2-was loaded on the surface of defective WO3 square nanoframes with abundant oxygen vacancies. The resulting nanocomposite exhibits a low overpotential of 191 mV at 10 mA cm−2 and a very low Tafel slope of 42 mV dec−1 toward hydrogen evolution reaction. The long-term cyclic voltammetry cycling of 5000 cycles and more than 80,000 s chronoamperometry tests promises its outstanding stability. The intimate and large interfacial contact between MoS2 and WO3, favoring the charge transfer and electron–hole separation by the synergy of defective WO3 and oxygen-incorporated MoS2, is believed the decisive factor for improving the electrocatalytic efficiency of the nanocomposite. Moreover, the defective WO3 nanoframes with plentiful oxygen vacancies could serve as an anisotropic substrate to promote charge transport and oxygen incorporation into the interface of MoS2. This work provides a unique methodology for designing and constructing excellently heterostructure electrocatalysts for hydrogen evolution reaction

Influence of Inorganic Additives on Pyrolysis of Pine Bark

This paper investigated the effect of inorganic additives on pine bark pyrolysis using a thermogravimetry instrument. Both thermogravimetry (TG) and differential thermogravimetry (DTG) were performed to a final temperature of 600 degrees C with heating rates of 10, 20, and 50 degrees C/min, respectively, and a nitrogen flow rate of 50 mL/min. Six types of inorganic additives at different loading were tested. The pyrolysis kinetics data of the samples were fitted to the Coats-Redfern model. The results showed that the pyrolysis behavior and kinetics are significantly altered by the additives and are a strong function of the characteristics and concentrations of the additives