Spontaneous spin current near the interface between unconventional superconductors and ferromagnets

We study theoretically the proximity effect between ferromagnets (F) and superconductors (S) with broken time-reversal symmetry (${\cal T}$). A chiral $(p_x\pm ip_y)$-wave, and a $d_{x^2-y^2}$-wave superconductor, the latter of which can form ${\cal T}$-breaking surface state, i.e., $(d_{x^2-y^2} \pm is)$-state, are considered for the S side. The spatial variations of the superconducting order parameters and the magnetization are determined by solving the Bogoliubov de Gennes equation. In the case of a chiral $(p_x\pm ip_y)$-wave superconductor, a spontaneous spin current flows along the interface, but not in the case of a $d_{x^2-y^2}$-wave superconductor. For F/S$(p_x+ip_y)$/F trilayer system, total spin current can be finite while total charge current vanishes, if the magnetization of two F layers are antiparallel.Comment: 6 pages, 11 figures. Accepted for publication in Physical Review

Effect of Band Structure on the Symmetry of Superconducting States

Effects of the band structure on the symmetry of superconducting (SC) states are studied. For a square lattice system with a nearest-neighbor attractive interaction, SC states with various symmetries are found by changing the band structure, or, the shape of the Fermi surface. The spin-triplet ($(p_x + ip_y)$-wave) and spin-singlet ($d$- or s-wave) SC states, and states with their coexistence ($d + ip_y$, $s + ip_y$) can be stabilized within the same type of interaction. The stability of interlayer-pairing states with line nodes is also examined, and its relation to the SC state of Sr$_2$RuO$_4$ is discussed.Comment: 4 pages, 4 figure

Ginzburg-Landau Equations for Coexistent States of Superconductivity and Antiferromagnetism in t-J model

Ginzburg-Landau (GL) equations for the coexistent state of superconductivity and antiferromagnetism are derived microscopically from the t-J model with extended transfer integrals. GL equations and the GL free energy, which are obtained based on the slave-boson mean-field approximation, reflect the electronic structure of the microscopic model, especially the evolution of the Fermi surface due to the change of the doping rate. Thus they are suitable for studying the material dependence of the coexistent states in high-$T_C$ cuprate superconductors.Comment: 12 page

Ground state of an S=1/2S=1/2 distorted diamond chain - model of Cu3Cl6(H2O)2⋅2H8C4SO2\rm Cu_3 Cl_6 (H_2 O)_2 \cdot 2H_8 C_4 SO_2

We study the ground state of the model Hamiltonian of the trimerized $S=1/2$ quantum Heisenberg chain $\rm Cu_3 Cl_6 (H_2 O)_2 \cdot 2H_8 C_4 SO_2$ in which the non-magnetic ground state is observed recently. This model consists of stacked trimers and has three kinds of coupling constants between spins; the intra-trimer coupling constant $J_1$ and the inter-trimer coupling constants $J_2$ and $J_3$. All of these constants are assumed to be antiferromagnetic. By use of the analytical method and physical considerations, we show that there are three phases on the $\tilde J_2 - \tilde J_3$ plane ($\tilde J_2 \equiv J_2/J_1$, $\tilde J_3 \equiv J_3/J_1$), the dimer phase, the spin fluid phase and the ferrimagnetic phase. The dimer phase is caused by the frustration effect. In the dimer phase, there exists the excitation gap between the two-fold degenerate ground state and the first excited state, which explains the non-magnetic ground state observed in $\rm Cu_3 Cl_6 (H_2 O)_2 \cdot 2H_8 C_4 SO_2$. We also obtain the phase diagram on the $\tilde J_2 - \tilde J_3$ plane from the numerical diagonalization data for finite systems by use of the Lanczos algorithm.Comment: LaTeX2e, 15 pages, 21 eps figures, typos corrected, slightly detailed explanation adde

Microscopic derivation of Ginzburg-Landau equations for coexistent states of superconductivity and magnetism

Ginzburg-Landau (GL) equations for the coexistent states of superconductivity and magnetism are derived microscopically from the extended Hubbard model with on-site repulsive and nearest-neighbor attractive interactions. In the derived GL free energy a cubic term that couples the spin-singlet and spin-triplet components of superconducting order parameters (SCOP) with magnetization exists. This term gives rise to a spin-triplet SCOP near the interface between a spin-singlet superconductor and a ferromagnet, consistent with previous theoretical studies based on the Bogoliubov de Gennes method and the quasiclassical Green's function theory. In coexistent states of singlet superconductivity and antiferromagnetism it leads to the occurrence of pi-triplet SCOPs.Comment: 18 page

Forming method and characteristics of coiled spring in small coil diameter and with high rectangular ratio in winding wire cross section

This paper presents a new forming method of a coiled spring which is used as a forceps manipulator of a surgical robot. Joint parts of forceps manipulator are required to be “easy to bend and strong to twist”. This demand is fulfilled by using coiled springs with high rectangular ratio in winding wire cross section. However, the coiled springs are conventionally expensive as they are fabricated by machining. This study proposed a new and inexpensive forming method for fabrication of the coiled spring with high rectangular ratio in the wire cross section. In this method, the coiled spring with circular shape in the winding wire cross section is compressed in the coil axial direction by upsetting, and then the rectangle ratio of the wire becomes high. The coiled spring with a high rectangular ratio of 3 was obtained by the proposed method. In addition, a numerical analysis and an experiment were conducted for evaluation of the formed coiled springs in terms of tensile, torsional, and bending characteristics. The formed coiled springs were easy to bend and strong to twist from results. Moreover, the elastic limit of the formed coiled springs improved due to work hardening by upsetting

OstemiR: A Novel Panel of MicroRNA Biomarkers in Osteoblastic and Osteocytic Differentiation from Mesencymal Stem Cells

　MicroRNAs (miRNAs) are small RNA molecules of 21–25 nucleotides that regulate cell behavior through inhibition of translation from mRNA to protein, promotion of mRNA degradation and control of gene transcription. In this study, we investigated the miRNA expression signatures of cell cultures undergoing osteoblastic and osteocytic differentiation from mesenchymal stem cells (MSC) using mouse MSC line KUSA-A1 and human MSCs. Ninety types of miRNA were quantified during osteoblastic/osteocytic differentiation in KUSA-A1 cells utilizing miRNA PCR arrays. Coincidently with mRNA induction of the osteoblastic and osteocytic markers, the expression levels of several dozen miRNAs including miR-30 family, let-7 family, miR-21, miR-16, miR-155, miR-322 and Snord85 were changed during the differentiation process. These miRNAs were predicted to recognize osteogenic differentiation-, stemness-, epinegetics-, and cell cycle-related mRNAs, and were thus designated OstemiR. Among those OstemiR, the miR-30 family was classified into miR-30b/c and miR-30a/d/e groups on the basis of expression patterns during osteogenesis as well as mature miRNA structures. In silico prediction and subsequent qRT-PCR in stable miR-30d transfectants clarified that context-dependent targeting of miR-30d on known regulators of bone formation including osteopontin/spp1, lifr, ccn2/ctgf, ccn1/cyr61, runx2, sox9 as well as novel key factors including lin28a, hnrnpa3, hspa5/grp78, eed and pcgf5. In addition, knockdown of human OstemiR miR-541 increased Osteopontin/SPP1 expression and calcification in hMSC osteoblastic differentiation, indicating that miR-541 is a negative regulator of osteoblastic differentiation. These observations indicate stage-specific roles of OstemiR especially miR-541 and the miR-30 family on novel targets in osteogenesis

OstemiR: A Novel Panel of MicroRNA Biomarkers in Osteoblastic and Osteocytic Differentiation from Mesencymal Stem Cells

MicroRNAs (miRNAs) are small RNA molecules of 21–25 nucleotides that regulate cell behavior through inhibition of translation from mRNA to protein, promotion of mRNA degradation and control of gene transcription. In this study, we investigated the miRNA expression signatures of cell cultures undergoing osteoblastic and osteocytic differentiation from mesenchymal stem cells (MSC) using mouse MSC line KUSA-A1 and human MSCs. Ninety types of miRNA were quantified during osteoblastic/osteocytic differentiation in KUSA-A1 cells utilizing miRNA PCR arrays. Coincidently with mRNA induction of the osteoblastic and osteocytic markers, the expression levels of several dozen miRNAs including miR-30 family, let-7 family, miR-21, miR-16, miR-155, miR-322 and Snord85 were changed during the differentiation process. These miRNAs were predicted to recognize osteogenic differentiation-, stemness-, epinegetics-, and cell cycle-related mRNAs, and were thus designated OstemiR. Among those OstemiR, the miR-30 family was classified into miR-30b/c and miR-30a/d/e groups on the basis of expression patterns during osteogenesis as well as mature miRNA structures. In silico prediction and subsequent qRT-PCR in stable miR-30d transfectants clarified that context-dependent targeting of miR-30d on known regulators of bone formation including osteopontin/spp1, lifr, ccn2/ctgf, ccn1/cyr61, runx2, sox9 as well as novel key factors including lin28a, hnrnpa3, hspa5/grp78, eed and pcgf5. In addition, knockdown of human OstemiR miR-541 increased Osteopontin/SPP1 expression and calcification in hMSC osteoblastic differentiation, indicating that miR-541 is a negative regulator of osteoblastic differentiation. These observations indicate stage-specific roles of OstemiR especially miR-541 and the miR-30 family on novel targets in osteogenesis

Phase diagram and critical properties of the frustrated Kondo necklace model in a magnetic field

The critical properties of the frustrated Kondo necklace model with a half saturation magnetization ($m=1/2$) have been studied by means of an exact-diagonalization method. It is shown from bosonization technique that the model can be effectively expressed as a quantum sine-Gordom model. Thus it may show three (dimer plateau, N{\'e}el plateau and Tomonaga-Luttinger liquid) phases due to competitions among the Ising anisotropy $\Delta$, and the nearest- and next-nearest-neighbor exchange interactions $J_1$ and $J_2$. The boundary lines on the $\Delta-J_2/J_1$ phase diagram separating the three phases are determined by the method of level spectroscopy based on the conformal field theory.Comment: 5 pages, 5 figure