Multipole ordering in f-electron systems

In order to investigate multipole ordering in f-electron systems from a microscopic viewpoint, we study the so-called \Gamma_8 models on three kinds of lattices, simple cubic (sc), bcc, and fcc, based on a j-j coupling scheme with f-electron hopping integrals through (ff\sigma) bonding. From the \Gamma_8 model, we derive an effective model for each lattice structure by using the second-order perturbation theory with respect to (ff\sigma). By further applying mean-field theory to the effective model, we find a \Gamma_{3g} antiferro-quadrupole transition for the sc lattice, a \Gamma_{2u} antiferro-octupole transition for the bcc lattice, and a longitudinal triple-q \Gamma_{5u} octupole transition for the fcc lattice.Comment: 2 pages, 3 figure

Phase structure of the large-N reduced gauge theory and generalized Weingarten model

We study a generalization of Weingarten model reduced to a point, which becomes the large-N reduced U(N) gauge theory in a special limit. We find that the U(1)^d symmetry is broken one by one, and restored simultaneously as U(1)^d -> U(1)^{d-1} -> ... -> U(1) -> 1 -> U(1)^d as we change the coupling constants. In this model we can develop an efficient algorithm and we can see the phase structure of large-N reduced model clearly, and therefore this model would be useful for the study of the unitary model.Comment: LaTeX-2e, 11 pages with 11 figures; typos correcte

Analysis of f-p model for octupole ordering in NpO2

In order to examine the origin of octupole ordering in NpO2, we propose a microscopic model constituted of neptunium 5f and oxygen 2p orbitals. To study multipole ordering, we derive effective multipole interactions from the f-p model by using the fourth-order perturbation theory in terms of p-f hopping integrals. Analyzing the effective model numerically, we find a tendency toward \Gamma_{5u} antiferro-octupole ordering.Comment: 4 pages, 3 figure

Microscopic theory of multipole ordering in NpO2

In order to examine the mysterious ordered phase of NpO2 from a microscopic viewpoint, we investigate an f-electron model on an fcc lattice constructed based on a j-j coupling scheme. First, an effective model with multipole interactions is derived in the strong-coupling limit. Numerical analysis of the model clearly indicates that the interactions for \Gamma_{4u} and \Gamma_{5u} moments are relevant to the ground state. Then, by applying mean-field theory to the simplified model including only such interactions, we conclude that longitudinal triple-q \Gamma_{5u} octupole order is realized in NpO2 through the combined effects of multipole interactions and anisotropy of the \Gamma_{5u} moment.Comment: 5 pages, 2 figure

Multipole Fluctuations in Filled Skutterudites

In order to clarify exotic multipole properties of filled skutterudites, we evaluate multipole susceptibility for $n$=1$\sim$5, where $n$ is the local $f$-electron number, on the basis of a multiorbital Anderson model constructed using the $j$-$j$ coupling scheme. For $n$=1, magnetic fluctuations dominate over low-temperature electronic properties, while for $n$=2 and 4, electronic states are dominated by both magnetic and quadrupole fluctuations. For $n$=3 and 5, octupole fluctuations are found to be significant, depending on the crystalline electric field potential. We discuss possible relevance of the results to actual materials.Comment: 4 pages, 3 figures, JPSJ2.cls. To be published in J. Phys. Soc. Jp

Glucan dendrimer for carbohydrate drugs

Dendrimers are highly branched and star-shaped polymers with nanometer-scale dimensions. The nanostructured macromolecules are known for their defined structures, versatility in drug delivery, and high functional properties similar to biomoleclules. We developed a new way to synthesize glucan dendrimer like glycogen by using branching enzyme (EC 2.4.1.18) and glucan phosphorylase (EC 2.4.1.1) by using glucose-1-phosphate as a substrate. This way enables us to produce glucan dendrimers with strictly controlled molecular size and branching structure. In this context, we developed specific glycosylation technology to substitute glucose residues at non-reducing ends with galactose, mannose, glucosamine, glucuronic acid, or N-acetylglucosamine residues. Glucose dendrimers having glucosamine and/or glucuronic acid residues are successfully used for conjugation of other functional molecules. The nano-particle conjugated glucan dendrimers with peptide antigen and nucleotide adjuvant is a potential platform for vaccine. We investigated the glucan dendrimers function as a drug carrier. The uptake of several glucose dendrimers into antigen-presenting cells (APCs), such as dendritic cell and macrophage, were examined. Glucose dendrimers were incorporated into APCs, and introducing various sugar moieties into glucan dendrimers enhance the uptake them by APCs. When glucan dendrimer-peptide conjugates were added to the cultured APCs, the peptides were effectively presented on the surface of APCs. FITC-labeled glucan dendrimers injected subcutaneously in mice accumulated into inguinal lymph nodes, which play important role to introduce acquired immune respons