Gutzwiller Projected wavefunctions in the fermonic theory of S=1 spin chains

We study in this paper a series of Gutzwiller Projected wavefunctions for S=1 spin chains obtained from a fermionic mean-field theory for general S>1/2 spin systems [Phys. Rev. B 81, 224417] applied to the bilinear-biquadratic (J-K) model. The free-fermion mean field states before the projection are 1D paring states. By comparing the energies and correlation functions of the projected pairing states with those obtained from known results, we show that the optimized Gutzwiller projected wavefunctions are very good trial ground state wavefunctions for the antiferromagnetic bilinear-biquadratic model in the regime K0). We find that different topological phases of the free-fermion paring states correspond to different spin phases: the weak pairing (topologically non-trivial) state gives rise to the Haldane phase, whereas the strong pairing (topologically trivial) state gives rise to the dimer phase. In particular the mapping between the Haldane phase and Gutwziller wavefunction is exact at the AKLT point K=1/3. The transition point between the two phases determined by the optimized Gutzwiller Projected wavefunction is in good agreement with the known result. The effect of Z2 gauge fluctuations above the mean field theory is analyzed.Comment: 10 pages,7 figure

Fractional Quantum Hall Effect in Topological Flat Bands with Chern Number Two

Recent theoretical works have demonstrated various robust Abelian and non-Abelian fractional topological phases in lattice models with topological flat bands carrying Chern number C=1. Here we study hard-core bosons and interacting fermions in a three-band triangular-lattice model with the lowest topological flat band of Chern number C=2. We find convincing numerical evidence of bosonic fractional quantum Hall effect at the $\nu=1/3$ filling characterized by three-fold quasi-degeneracy of ground states on a torus, a fractional Chern number for each ground state, a robust spectrum gap, and a gap in quasihole excitation spectrum. We also observe numerical evidence of a robust fermionic fractional quantum Hall effect for spinless fermions at the $\nu=1/5$ filling with short-range interactions.Comment: 5 pages, 7 figures, with Supplementary Materia

Abnormal magnetoresistance behavior in Nb thin film with rectangular antidot lattice

Abnormal magnetoresistance behavior is found in superconducting Nb films perforated with rectangular arrays of antidots (holes). Generally magnetoresistance were always found to increase with increasing magnetic field. Here we observed a reversal of this behavior for particular in low temperature or current density. This phenomenon is due to a strong 'caging effect' which interstitial vortices are strongly trapped among pinned multivortices.Comment: 4 pages, 2 figure

Pseudogap, Superconducting Energy Scale, and Fermi Arcs in Underdoped Cuprate Superconductors

Through the measurements of magnetic field dependence of specific heat in $La_{2-x}Sr_xCuO_4$ in zero temperature limit, we determined the nodal slope $v_\Delta$ of the quasiparticle gap. It is found that $v_\Delta$ has a very similar doping dependence of the pseudogap temperature $T^*$ or value $\Delta_p$. Meanwhile the virtual maximum gap at ($\pi,0$) derived from $v_\Delta$ is found to follow the simple relation $\Delta_q=0.46k_BT^*$ upon changing the doping concentration. This strongly suggests a close relationship between the pseudogap and superconductivity. It is further found that the superconducting transition temperature is determined by both the residual density of states of the pseudogap phase and the nodal gap slope in the zero temperature limit, namely, $T_c \approx \beta v_\Delta \gamma_n(0)$, where $\gamma_n(0)$ is the extracted zero temperature value of the normal state specific heat coefficient which is proportional to the size of the residual Fermi arc $k_{arc}$. This manifests that the superconductivity may be formed by forming a new gap on the Fermi arcs near nodes below $T_c$. These observations mimic the key predictions of the SU(2) slave boson theory based on the general resonating-valence-bond (RVB) picture.Comment: 6 pages, 6 figures, to be published in Phys. Rev.

Phenomenological Scaling of Rapidity Dependence for Anisotropic Flows in 25 MeV/nucleon Ca + Ca by Quantum Molecular Dynamics Model

Anisotropic flows ($v_1$, $v_2$, $v_3$ and $v_4$) of light fragments up till the mass number 4 as a function of rapidity have been studied for 25 MeV/nucleon $^{40}$Ca + $^{40}$Ca at large impact parameters by Quantum Molecular Dynamics model. A phenomenological scaling behavior of rapidity dependent flow parameters $v_n$ (n = 1, 2, 3 and 4) has been found as a function of mass number plus a constant term, which may arise from the interplay of collective and random motions. In addition, $v_4/{v_2}^2$ keeps almost independent of rapidity and remains a rough constant of 1/2 for all light fragments.Comment: 4 pages, 5 figure

Growth, ion content and photosynthetic responses of two Elytrigia Desv. species seedlings to salinity stress

Salinity is among the major abiotic stresses limiting crop production in the world. Elytrigia species, the wild relatives of wheat, are extensively used as genetic resources in wheat breeding to improve its salt tolerance. The objective of this study was to examine the responses to different NaCl treatments (0, 65, 100, 135 and 170 mM) of two Elytrigia species (Elytrigia intermedia (Host.) Nevski. and Elytrigia trichophora (Link.) Nevski.) in terms of their growth, ion content and photosynthetic productivity during the seedling stages. For E. intermedia, salt treatment led to decreases in root and shoot biomass, chlorophyll content, photosynthetic rate (A) and stomatal conductance (gs), and a concurrent increase in intercellular CO2 concentration (Ci). Larger reductions in the parameters occurred in E. trichophora. Our results indicated that the two species differ in their sensitivity to salinity, with E. intermedia being classified as the more salt tolerant, and E. trichophora as sensitive. The two species also differed noticeably in leaf tissue concentrations of Na+ and K+ at various NaCl treatments, although, they both showed a trend for Na+ content to increase and K+ accumulation to significantly decrease in the higher salinity treatments.Key words: Elytrigia, ion contents, photosynthesis, salinity

Growth and physiological response of tall oat grass to salinity stress

In order to evaluate the responses of tall oat grass plants to increasing salinity, we measured plant growth, ion contents, photosynthetic gas exchange, lipid peroxidation, and proline accumulation in four salt concentrations. Two tall oatgrass genotypes, ZXY03P-367 and ZXY03P-443, were grown for 14 days in greenhouse conditions and after 14 days treated with four NaCl treatments (0, 65, 100, and 135 mM ) for 21 days. Most parameters for the two genotypes were significantly different when they were subjected to 100 and 135 mM NaCl. Salt treatment led to decreases in root and shoot biomass, photosynthetic rate (A) and stomatal conductance (gs), and K+ content, and a concurrent increase in Na+ content. Larger reductions in the parameters occurred in ZXY03P-443. A significant accumulation of lipid peroxidation and proline in leaves was found during the period of intensive leaf growth. These organic compounds likely played a role in leaf osmotic adjustment and in the protection of membrane stability at severe salinity levels. Our results indicated that the two tall oatgrass genotypes differ in their sensitivity to salinity, with ZXY03P-336 classified as relatively salt tolerant and ZXY03P-443 as  sensitive.Key words: Growth, physiological responses, salinity stress, tall oatgras

Effect of gauge boson mass on the phase structure of QED3_{3}

Dynamical chiral symmetry breaking (DCSB) in QED$_{3}$ with finite gauge boson mass is studied in the framework of the rainbow approximation of Dyson-Schwinger equations. By adopting a simple gauge boson propagator ansatz at finite temperature, we first numerically solve the Dyson-Schwinger equation for the fermion self-energy to determine the chiral phase diagram of QED$_3$ with finite gauge boson mass at finite chemical potential and finite temperature, then we study the effect of the finite gauge mass on the phase diagram of QED$_3$. It is found that the gauge boson mass $m_{a}$ suppresses the occurrence of DCSB. The area of the region in the chiral phase diagram corresponding to DCSB phase decreases as the gauge boson mass $m_{a}$ increases. In particular, chiral symmetry gets restored when $m_{a}$ is above a certain critical value. In this paper, we use DCSB to describe the antiferromagnetic order and use the gauge boson mass to describe the superconducting order. Our results give qualitatively a physical picture on the competition and coexistence between antiferromagnetic order and superconducting orders in high temperature cuprate superconductors.Comment: 10 pages, 2 figure