Vacuum induced Berry phases in single-mode Jaynes-Cummings models

Motivated by the work [Phys. Rev. Lett. 89, 220404 (2002)] for detecting the vacuum-induced Berry phases with two-mode Jaynes-Cummings models (JCMs), we show here that, for a parameter-dependent single-mode JCM, certain atom-field states also acquire the photon-number-dependent Berry phases after the parameter slowly changed and eventually returned to its initial value. This geometric effect related to the field quantization still exists, even the filed is kept in its vacuum state. Specifically, a feasible Ramsey interference experiment with cavity quantum electrodynamics (QED) system is designed to detect the vacuum-induced Berry phase.Comment: 10 pages, 4 figures

On the Convergence of Ritz Pairs and Refined Ritz Vectors for Quadratic Eigenvalue Problems

For a given subspace, the Rayleigh-Ritz method projects the large quadratic eigenvalue problem (QEP) onto it and produces a small sized dense QEP. Similar to the Rayleigh-Ritz method for the linear eigenvalue problem, the Rayleigh-Ritz method defines the Ritz values and the Ritz vectors of the QEP with respect to the projection subspace. We analyze the convergence of the method when the angle between the subspace and the desired eigenvector converges to zero. We prove that there is a Ritz value that converges to the desired eigenvalue unconditionally but the Ritz vector converges conditionally and may fail to converge. To remedy the drawback of possible non-convergence of the Ritz vector, we propose a refined Ritz vector that is mathematically different from the Ritz vector and is proved to converge unconditionally. We construct examples to illustrate our theory.Comment: 20 page

Electron quantum interference in epitaxial antiferromagnetic NiO thin films

The electron reflectivity from NiO thin films grown on Ag(001) has been systematically studied as a function of film thickness and electron energy. A strong electron quantum interference effect was observed from the NiO film, which is used to derive the unoccupied band dispersion above the Fermi surface along the Γ-X direction using the phase accumulation model. The experimental bands agree well with first-principles calculations. A weaker electron quantum interference effect was also observed from the CoO film

Using aeration and insulation to reduce grain temperature in China grain warehouses

Reducing grain temperature is a safe, effective and economic way to minimize damage to grain. It suppresses the activity of all life forms in a grain storage ecosystem. As a result, it stabilizes the grain during storage, reduces loss and keeps freshness. We conducted trials on grain storage facilities (2800-8000 t) in Tianjin, China. The technologies are based on the following factors: the characteristics of local climate (cold dry winters and hot humid summers), large scale storage structure and grain special requirements. Based on these factors, the researchers devised comprehensive and targeted solutions. For example, the insulation of existing large flat top storage was increased, by using various insulation materials in exterior roofing, interior ceiling, walls, vents, windows and doors, using efficient yet economic insulation material in new storage construction. In winter, we used ventilation by natural and forced aeration to maintain low temperatures. In summer, we used insulation and cooling to achieve temperature control. The technology can effectively reduce grain losses and maintain quality by reducing grain respiration, insect and microbial activities. At the same time, it reduces and avoids chemical pollution, protects the grain and the environment from pollution. It achieves low grain loss, low environmental impact, lower cost; high grain quality, high grain nutrient and high efficiency. It is becoming a new direction in scientific grain storage. Keywords: Temperature controlled grain storage, Tianjin, Chin

Seismic performance of a load-bearing prefabricated composite wall panel structure for residential construction

To improve both seismic performance and thermal insulation of low-rise housing in rural areas of China, this study proposes a load-bearing prefabricated composite wall panel structure that achieves appropriate seismic performance and energy efficiency using field-assembled load-bearing prefabricated composite wall panels. A 1:2 scale prototype built using load-bearing prefabricated composite wall panel is subjected to quasi-static testing so as to obtain damage characteristics, load-bearing capacity and load–displacement curves in response to a simulated earthquake. As a result, seismic performance indicators of load-bearing capacity, deformation and energy-dissipating characteristics, are assessed against the corresponding seismic design requirements for rural building structures of China. Experimental results indicate that the earthquake-resistant capacity of the prototype is 68% higher than the design value. The sample has a ductility factor of 4.7, which meets the seismic performance requirement mandating that the ductility factor of such concrete structures should exceed 3. The design can be further optimized to save the consumption of material. This shows that the load-bearing prefabricated composite wall panel structure developed here has decent load-bearing capacity, ductility and energy dissipation abilities, a combination of which is in line with the seismic design code. A new construction process proposed here based on factory prefabrication and field assembly leads to a considerable reduction of energy consumption. </jats:p

Two-dimensional Superconductivity from Dimerization of Atomically Ordered AuTe2Se4/3 Cubes

The emergent phenomena such as superconductivity and topological phase transitions can be observed in strict two-dimensional crystalline matters. Artificial interfaces and one atomic thickness layers are typical 2D materials of this kind. Although having 2D characters, most bulky layered compounds, however, do not possess these striking properties. Here, we report the 2D superconductivity in bulky AuTe2Se4/3,where the reduction in dimensionality is achieved through inducing the elongated covalent Te-Te bonds. The atomic-resolution images reveal that the Au, Te and Se are atomically ordered in a cube, among which are Te-Te bonds of 3.18 A and 3.28 A. The superconductivity at 2.85 K is discovered, which is unraveled to be the quasi-2D nature owing to the BKT topological transition. The nesting of nearly parallel Fermi sheets could give rise to strong electron-phonon coupling. It is proposed to further depleting the thickness could result in more topologically-related phenomena.Comment: 16 pages, 5 figures,To be published in Nature Communication