Large-Gap Quantum Anomalous Hall Insulators in AATiXX Class

We theoretically propose that the monolayer $A$Ti$X$ family (KTiSb, KTiBi, RbTiSb, SrTiSn) are potential candidates for large-gap quantum anomalous Hall insulators with high Chern number $\mathcal{C}=2$. Both of the topology and magnetism in these materials are from $3d$-orbitals of Ti. We construct the tight-binding model with symmetry analysis to reveal the origin of topology. Remarkably, quite different from the conventional $s$-$d$ band inversion, here the topological band inversion within $3d$ orbitals is due to the crystal field and electron hopping, while spin-orbit coupling only trivially gaps out the Dirac cone at Fermi level. The general physics from the $3d$ orbitals here applies to a large class of transition metal compounds with the space group $P4/nmm$ or $P$-$42m$ and their subgroups.Comment: 6 pages, 4 figure

Expression of syndecan-1 in the retina of diabetes

AIM:To observe the expression of syndecan-1 on epiretinal membranes obtained from patients with proliferative diabetic retinopathy and retina of diabetic rats. METHODS:SD rats were given intraperitoneal injection of streptozotocin to induce diabetes. Ink perfusion and stretched retina were used to observe the retinal blood vessels. Immunohistochemistry staining was used to detect syndecan-1 protein in the rat retina and epiretinal membranes of proliferative diabetic retinopathy. RESULTS:In the diabetic rats of 9-week, peripheral retinal blood vessels shaped tortuously, capillary network was significantly reduced, and parts of the capillary perfusion was bad. In the control group, strong positive staining of syndecan-1 was detected in the nerve fiber layer and ganglion cells, moderate positive staining was observed in the inner plexiform layer and outer segments of photoreceptor, and weak positive staining was detected in the outer plexiform layer. In the retina of diabetic rats, syndecan-1 decreased. Moderate positive staining of syndecan-1 was observed in the nerve fiber layer, ganglion cells and outer segments of photoreceptor, weak positive staining was detected in the inner plexiform layer and outer plexiform layer. Among 13 specimens of epiretinal membranes, weak positive staining of syndecan-1 was detected in 8 cases(61.5%)and negative staining was observed in 5 cases(38.5%). CONCLUSION:Syndecan-1 is down-regulated in the retina of diabetic rats and epiretinal membranes of proliferative diabetic retinopathy

Giant anisotropic band flattening in twisted Γ\Gamma valley semiconductor bilayers

We propose a theory of anisotropic band flattening in moir\'e systems at the $\Gamma$ valley. We find that in twisted anisotropic two-dimensional crystals with a rectangular unit cell of $C_{2z}$ or mirror symmetries, a larger effective mass anisotropy $\eta=m_y/m_x$ has a stronger tendency to be further enhanced compared to that of monolayer, which leads to correlated physics in one dimension effectively. We predict twisted bilayer black phosphorus (tBBP) has giant anisotropic flattened moir\'e bands ($\eta\sim10^4$) from ab initio calculations and continuum model, where the low energy physics is described by the weakly coupled array of one-dimensional wires. We further calculate the phase diagram based on sliding Luttinger liquid by including the screened Coulomb interactions in tBBP, and find a large parameter space may host the non-Fermi liquid phase. We thus establish tBBP as a promising and experimentally accessible platform for exploring correlated physics in low dimensions.Comment: 5 pages, 4 figure

Concession Period Decision Models for Public Infrastructure Projects Based on Option Games

Concession period is an important decision-making variable for the investment and construction of public infrastructure projects. However, we currently have few scientific methods to exactly determine the concession period. This paper managed to seek out concession period decision models for public infrastructure with option game theory, studied the influence of minimum government income guarantee and government investment on concession period, and demonstrated those models in the formulas mentioned in the paper. The research results showed that the increase of minimum government income guarantee value would shorten the concession period, while the increase of income volatility, that is, the uncertainty, would lengthen the concession period. In terms of government investment, optimal concession period would lengthen to some extent with the increase of government investment ratio and the income and the decrease of its guarantee value. Yet, optimal concession period would shorten in case of extreme highness of the government investment ratio due to its high guarantee value. And the government would accordingly shorten the concession period in case of the unchanged government investment ratio with the increased income volatility and risks. Still, the paper put forward the argument that the government would apply various guarantee methods and implement flexible concession period in accordance with the specific circumstances of public infrastructure projects

Intrinsic antiferromagnetic topological insulator and axion state in V2WS4

Intrinsic magnetic topological insulators offers an ideal platform to explore exotic topological phenomena, such as axion electrodynamics, quantum anomalous Hall (QAH) effect and Majorana edge modes. However, these emerging new physical effects have rarely been experimentally observed due to the limited choice of suitable materials. Here, we predict the van der Waals layered V$_2$WS$_4$ and its related materials show intralayer ferromagnetic and interlayer antiferromagnetic exchange interactions. We find extremely rich magnetic topological states in V$_2$WS$_4$, including an antiferromagnetic topological insulator, the axion state with the long-sought quantized topological magnetoelectric effect, three-dimensional QAH state, as well as a collection of QAH insulators and intrinsic axion insulators in odd- and even-layer films, respectively. Remarkably, the N\'eel temperature of V$_2$WS$_4$ is predicted to be much higher than that of MnBi$_2$Te$_4$. These interesting predictions, if realized experimentally, could greatly promote the topological quantum physics research and application.Comment: 7 pages, 4 figure

Fitting magnetic field gradient with Heisenberg-scaling accuracy

We propose a quantum fitting scheme to estimate the magnetic field gradient with $N$-atom spins preparing in W state, which attains the Heisenberg-scaling accuracy. Our scheme combines the quantum multi-parameter estimation and the least square linear fitting method to achieve the quantum Cram\'{e}r-Rao bound (QCRB). We show that the estimated quantity achieves the Heisenberg-scaling accuracy. In single parameter estimation with assumption that the magnetic field is strictly linear, two optimal measurements can achieve the identical Heisenberg-scaling accuracy. Proper interpretation of the super-Heisenberg-scaling accuracy is presented. The scheme of quantum metrology combined with data fitting provides a new method in fast high precision measurements.Comment: 7 pages, 2 figure