The effects of optically induced non-Abelian gauge field in cold atoms

We show that $N-1$ degenerate dark states can be generated by coupling $N$-fold degenerate ground states and a common excited state with $N$ laser fields. Interferences between light waves with different frequencies can produce laser fields with time-dependent amplitudes, which can induce not only U(N) non-Abelian vector fields but also the scalar ones for the adiabatic motion of atoms in such laser fields. As an example, a time-periodic gauge potential is produced by applying specific laser fields to a tripod system. Some features of the Landau levels and the ground-state phase diagram of a rotating Bose-Einstein condensate for a concrete gauge field are also discussed.Comment: Revtex 6 pages, 2 figures, version to be published in PR

Kinetic Ballooning Mode Under Steep Gradient: High Order Eigenstates and Mode Structure Parity Transition

The existence of kinetic ballooning mode (KBM) high order (non-ground) eigenstates for tokamak plasmas with steep gradient is demonstrated via gyrokinetic electromagnetic eigenvalue solutions, which reveals that eigenmode parity transition is an intrinsic property of electromagnetic plasmas. The eigenstates with quantum number $l=0$ for ground state and $l=1,2,3\ldots$ for non-ground states are found to coexist and the most unstable one can be the high order states ($l\neq0$). The conventional KBM is the $l=0$ state. It is shown that the $l=1$ KBM has the same mode structure parity as the micro-tearing mode (MTM). In contrast to the MTM, the $l=1$ KBM can be driven by pressure gradient even without collisions and electron temperature gradient. The relevance between various eigenstates of KBM under steep gradient and edge plasma physics is discussed.Comment: 6 pages, 6 figure

Conversion of 40^{40}K-87^{87}Rb mixtures into stable molecules

We study the conversion of $^{40}$K and $^{87}$Rb atoms into stable molecules through the stimulated Raman adiabatic passage (STIRAP) in photoassociation assisted with Feshbach resonance. Starting with the mean-field Langrange density, we show that the atom-to-molecule conversion efficiency by STIRAP aided by Feshbach resonance is much larger than that by bare Feshbach resonance. We also study the influence of the population imbalance on the atom-to-molecule conversion.Comment: Revtex, 5 pages, 3 figures; version to appear in PRA (some content changed

The role of inter-well tunneling strength on coherence dynamics of two-species Bose-Einstein condensates

Coherence dynamics of two-species Bose-Einstein condensates in double wells is investigated in mean field approximation. We show that the system can exhibit decoherence phenomena even without the condensate-environment coupling and the variation tendency of the degree of coherence depends on not only the parameters of the system but also the initial states. We also investigate the time evolution of the degree of coherence for a Rosen-Zener form of tunneling strength, and propose a method to get a condensate system with certain degree of coherence through a time-dependent tunneling strength

Boron Nitride Nanosheets for Metal Protection

Although the high impermeability of graphene makes it an excellent barrier to inhibit metal oxidation and corrosion, graphene can form a galvanic cell with the underlying metal that promotes corrosion of the metal in the long term. Boron nitride (BN) nanosheets which have a similar impermeability could be a better choice as protective barrier, because they are more thermally and chemically stable than graphene and, more importantly, do not cause galvanic corrosion due to their electrical insulation. In this study, the performance of commercially available BN nanosheets grown by chemical vapor deposition as a protective coating on metal has been investigated. The heating of the copper foil covered with the BN nanosheet at 250 {\deg}C in air over 100 h results in dramatically less oxidation than the bare copper foil heated for 2 h under the same conditions. The electrochemical analyses reveal that the BN nanosheet coating can increase open circuit potential and possibly reduce oxidation of the underlying copper foil in sodium chloride solution. These results indicate that BN nanosheets are a good candidate for oxidation and corrosion protection, although conductive atomic force microscopy analyses show that the effectiveness of the protection relies on the quality of BN nanosheets.Comment: With Supporting Informatio

Ideias de governança em Kong-Zi Jiayu e seus valores contemporâneos

Kong-Zi Jia Yu is a book that recorded many Confucius and his disciples’ conversations and thoughts, making it an indispensable source to explore traditional Chinese culture and ideas. In particular, the governance ideas presented in the book are still highly relevant today. People-oriented thoughts were the core of governance wisdom, paradigmatic kingcraft and virtuous courtiers were a sensible part of governance, and the penological ideas further ensured the robust operations of it. In the new era, new ideas like “putting the people as the top priority”, Xi Jinping’s thoughts on building cadre teams and governing China by the rule of law have successively proposed as creative converts and innovative development of Chinese culture that has been carried forward over thousands of years. Inheriting and promoting these cultural "genes", refining their ideological essence, are of great reference value for cultivating the current political landscape, enriching the connotation of the construction of the cadre team in the new era, adhering to the rule of law and providing ideas for the formulation of current rural governance policies.Kong-Zi Jia Yu é um livro que registrou muitas conversas e pensamentos de Confúcio e de seus discípulos, tornando-o uma fonte indispensável para explorar a cultura e as ideias tradicionais chinesas. Em particular, as ideias de governança apresentadas no livro ainda são altamente relevantes hoje. Os pensamentos orientados para as pessoas eram o núcleo da sabedoria da governação, a realeza paradigmática e os cortesãos virtuosos eram uma parte sensata da governança, e as ideias penológicas asseguravam ainda mais as operações robustas da mesma. Na nova era, novas ideias como “colocar o povo como prioridade máxima”, os pensamentos de Xi Jinping sobre a construção de equipas de quadros e governar a China pelo Estado de direito foram sucessivamente propostos como conversões criativas e desenvolvimento inovador da cultura chinesa que foi levado adiante ao longo de milhares de anos. Herdar e promover estes “genes” culturais, refinando a sua essência ideológica, são de grande valor de referência para cultivar o panorama político atual, enriquecendo a conotação da construção da equipa de quadros na nova era, aderindo ao Estado de direito e fornecendo ideias para a formulação das actuais políticas de governação rural