Site-selective insulating phase in twisted bilayer Hubbard model

The paramagnetic phase diagrams of the half-filled Hubbard model on a twisted bilayer square lattice are investigated using coherent potential approximation. Besides the conventional metallic, band insulating, and Mott insulating phases, we find two site-selective insulating phases where certain sites exhibit band insulating behaviors while the others display Mott insulating behaviors. These phases are identified by the band gap, the double occupancy, the density of states, as well as the imaginary part of self-energy. Furthermore, we examine the effect of on-site potential on the stability of the site-selective insulating phases. Our results indicate that fruitful site-selective phases can be engineered by twisting.Comment: 12 pages, 6 figure

An improved particle swarm optimization algorithm and its application to search for new magnetic ground states in the Hubbard model

An improved particle swarm optimization algorithm is proposed and its superiority over standard particle swarm optimization algorithm is tested on two typical benchmark functions. By employing this algorithm to search for the magnetic ground states of the Hubbard model on the real-space square lattice with finite size based on the mean-field approximation, two new magnetic states, namely the double striped-type antiferromagnetic state and the triple antiferromagnetic state, are found. We further perform mean-field calculations in the thermodynamical limit to confirm that these two new magnetic states are not a result of a finite-size effect, where the properties of the double striped-type antiferromagnetic state are also presented.Comment: 8 pages, 7 figure

Comparison of corneal flap thickness using a FS200 femtosecond laser and a moria SBK microkeratome

<b>AIM:</b> To evaluate differences in flap thickness resulting from use of an Alcon Wavelight FS200 femtosecond laser and a MORIA SBK microkeratome when making a 110-μm-thick corneal flap and to identify the potential factors that affect corneal flap thickness.<b>METHODS:</b> A prospective case study was performed on 120 eyes of 60 patients who were divided into two groups for LASIK, each group consisting of 60 eyes (30 patients). The corneal flaps were created using an Alcon Wavelight FS200 femtosecond laser or a MORIA SBK microkeratome. The central corneal flap thickness was calculated by subtraction pachymetry. Age, central corneal thickness (CCT), spherical equivalent refraction, mean keratometry, and corneal diameter were recorded preoperatively for analysis.<b>RESULTS:</b> Cutting of all flaps was easily performed without intraoperative complications. In the Alcon Wavelight FS200 femtosecond lasergroup, the mean right and left corneal flap thicknesses were 114.0±6.6 μm (range:98-126) and 111.4±7.6 μm (range:98-122), respectively. The difference (2.6±9.1 μm) in the corneal flap thickness between the right and left eyes was not significant (<i>t</i>=1.59, <i>P</i>=0.12). Stepwise regression analysis indicated that the resulting corneal flap thickness was unrelated to the patient’s age, preoperative CCT, spherical equivalent refraction, mean keratometry, or corneal diameter. In the MORIA SBK microkeratome group, the mean right and left corneal flap thicknesses were 110.6±7.4 μm (range:97-125 μm) and 108.2±6.1 μm (range:78-123 μm), respectively. The difference in the corneal flap thickness between the right and left eyes (2.4±6.5μm) was not significant (<i>t</i>=2.039, <i>P</i>=0.0506). The corneal flap thickness was positively correlated with the preoperative CCT through stepwise regression analysis (<i>r</i>=0.297,<i> P</i>=0.021). The corneal flap thickness was not related to age, spherical equivalent refraction, mean keratometry, or corneal diameter. The corneal flap thickness was estimated using the following equation:Tflap=67.77+0.076 CCT (<i>F</i>=5.63, <i>P</i>=0.021).<b>CONCLUSION:</b>Both the Alcon Wavelight FS200 femtosecond laser and the MORIA SBK microkeratome produced 110-μm-thick corneal flaps. The central corneal flap thickness was positively correlated with the preoperative CCT in MORIA SBK microkeratome surgery

Generating Irregular Models for 3D Spherical-Particle-Based Numerical Methods

The realistic representation of an irregular geological body is essential to the construction of a particle simulation model. A three-dimensional (3D) sphere generator for an irregular model (SGIM), which is based on the platform of Microsoft Foundation Classes (MFC) in VC++, is developed to accurately simulate the inherent discontinuities in geological bodies. OpenGL is employed to visualize the modeling in the SGIM. Three key functions, namely, the basic-model-setup function, the excavating function, and the cutting function, are implemented. An open-pit slope is simulated using the proposed model. The results demonstrate that an extremely irregular 3D model of a geological body can be generated using the SGIM and that various types of discontinuities can be inserted to cut the model. The data structure of the model that is generated by the SGIM is versatile and can be easily modified to match various numerical calculation tools. This can be helpful in the application of particle simulation methods to large-scale geoengineering projects