Orbital density wave induced by electron-lattice coupling in orthorhombic iron pnictides

In this paper we explore the magnetic and orbital properties closely related to a tetragonal-orthorhombic structural phase transition in iron pnictides based on both two- and five-orbital Hubbard models. The electron-lattice coupling, which interplays with electronic interaction, is self-consistently treated. Our results reveal that the orbital polarization stabilizes the spin density wave (SDW) order in both tetragonal and orthorhombic phases. However, the ferro-orbital density wave (F-ODW) only occurs in the orthorhombic phase rather than in the tetragonal one. Magnetic moments of Fe are small in the intermediate Coulomb interaction region for the striped antiferromangnetic phase in the realistic five orbital model. The anisotropic Fermi surface in the SDW/ODW orthorhombic phase is well in agreement with the recent angle-resolved photoemission spectroscopy experiments. These results suggest a scenario that the magnetic phase transition is driven by the ODW order mainly arising from the electron-lattice coupling.Comment: 21 pages, 10 figure

Isolation and characterization of an Aux/IAA gene (LaIAA2) from Larix

The phytohormone auxin controls many aspects of plant development. Auxin/indole-3-acetic acid (Aux/IAA)  transcriptional factors are key regulators of auxin responses in plants. To investigate the effects of auxin on  gene expression during the rooting process of Larix cuttings, a subtractive cDNA library was constructed and  272 UniEST were obtained by using suppression subtractive hybridization (SSH). Based on a fragment of 272  UniEST, the full-length cDNA of LaIAA2, an Aux /IAA gene from Larix was isolated. Then, the response  expression of LaIAA2 to auxin was determined by treating with different sources and concentration of auxin and cycloheximide and the expression patterns of LaIAA2 were examined in different tissues. The results show  that LaIAA2 appears to be the first response gene of auxin and LaIAA2 gene was involved in the root  development and auxin signaling. The express pattern of LaIAA2 gene indicated that it might play a central role in root development, specially regulated lateral and adventitious root production.Key words: Aux/IAA gene family, auxin, LaIAA2, Lari

Geometric phase driven Josephson junction: Possible experimental scheme for the search of spin superfluidity

We use the Gross-Pitaevskii equation to study Josephson tunneling between two weakly coupled Bose-Einstein condensates, which compose spin-1 bosons. We show that a rotating magnetic field on one side can produce a phase difference across the junction, resulting in an oscillatory tunneling spin current. Besides numerical calculation, we derive analytical results in two extreme cases, namely the low- and high-frequency limits: in the low-frequency limit (magnetic field rotates adiabatically), a non-Abelian geometric phase arises and leads to the oscillatory spin current. By sharp contrast, the physics is intrinsically different in the high-frequency limit, where an average Zeeman energy difference leads to an oscillatory spin current. This proposed apparatus should be promising for the future experimental search of spin superfluidity.Comment: 14 pages, 8 figures. Published version. Title changed. Comments are welcom