TRAF6-NFкB pathway in cell growth and differentiation

[Curriculum Vitae & Summary] International Symposium on Tumor Biology in Kanazawa 2004 / Kanazawa, Japan February 12 and 13, 200

Electrically controlled superconducting states at the heterointerface SrTiO3_3/LaAlO3_3

We study the symmetry of Cooper pair in a two-dimensional Hubbard model with the Rashba-type spin-orbit interaction as a minimal model of electron gas generated at a heterointerface of SrTiO$_3$/LaAlO$_3$. Solving the Eliashberg equation based on the third-order perturbation theory, we find that the gap function consists of the mixing of the spin-singlet $d_{xy}$-wave component and the spin-triplet $(p_x\pm ip_y)$-wave one due to the broken inversion symmetry originating from the Rashba-type spin-orbit interaction. The ratio of the d-wave and the p-wave component continuously changes with the carrier concentration. We propose that the pairing symmetry is controlled by tuning the gate voltage.Comment: 4 pages, 4 figures; added reference

Incommensurate--commensurate transitions in the mono-axial chiral helimagnet driven by the magnetic field

The zero temperature phase diagram of the mono-axial chiral helimagnet in the magnetic field plane formed by the components parallel and perpendicular to the helical axis is thoroughly analyzed. The nature of the transition to the commensurate state depends on the angle between the field and the helical axis. For field directions close to the directions parallel or perpendicular to the helical axis the transition is continuous, while for intermediate angles the transition is discontinuous and the incommensurate and commensurate states coexist on the transition line. The continuous and discontinuous transition lines are separated by two tricritical points with specific singular behaviour. The location of the continuous and discontinuous lines and of the tricritical points depend strongly on the easy-plane anisotropy, the effect of which is analyzed. For large anisotropy the conical approximation locates the transition line very accurately, although it does not predict the continuous transitions nor the tricitical behaviour. It is shown that for large anisotropy, as in CrNb3S6, the form of the transition line is universal, that is, independent of the sample, and obeys a simple equation. The position of the tricritical points, which is not universal, is theoretically estimated for a sample of CrNb3S6Comment: 10 pages, 9 figure

Current-induced shuttlecock-like movement of non-axisymmetric chiral skyrmions

Current-induced motion of non-axisymmetric skyrmions within tilted ferromagnetic phases of polar helimagnets with the easy plane anisotropy is studied by micromagnetic simulations. Such non-axisymmetric skyrmions consist of a circular core and a crescent-shaped domain-wall region formed with respect to the tilted surrounding state. Current-driven motion of non-axisymmetric skyrmions exhibits two distinct time regimes: initially the skyrmions rotate towards the current flow direction and subsequently move along the current with the skyrmionic crescent first. According to the Thiele equation, the asymmetric distribution of the topological charge and the dissipative force tensor play an important role for giving the different velocities for the circular and the crescent-shaped constituent parts of the skyrmion what underlies such a shuttlecock-like movement. Moreover, the current-velocity relation depends on the angle of the tilted ferromagnetic phase what makes in particular the transverse velocity of skyrmions sensitive to their field-driven configurational transformation. We also argue the possibility of magnetic racetrack waveguides based on complex interplay of robust asymmetric skyrmions with multiple twisted edge states

Meissner effect in diffusive normal metal/superconductor junctions

Meissner effect in the diffusive normal metal/insulator/s-wave superconductor junctions is studied in the presence of the magnetic impurities for various situations, where we have used the Usadel equation with Nazarov’s generalized boundary condition. It is shown that the susceptibility of the diffusive normal metal for s-wave superconductor is almost independent of the height of the insulating barrier at the interface

Vertex Corrections on the Anomalous Hall Effect in Spin-polarized Two-dimensional Electron Gases with Rashba Spin-orbit Interaction

We study the effect of disorder on the intrinsic anomalous Hall (AH) conductivity in a spin-polarized two-dimensional electron gas with a Rashba-type spin-orbit interaction. We find that AH conductivity vanishes unless the lifetime is spin-dependent, similar to the spin Hall (SH) conductivity in the non-magnetic system. In addition, we find that the SH conductivity does not vanish in the presence of magnetic scatterers. We show that the SH conductivity can be controlled by changing the amount of the magnetic impurities.Comment: Tex file only, no figure

Predominant Magnetic States in Hubbard Model on Anisotropic Triangular Lattices

Using an optimization variational Monte Carlo method, we study the half-filled-band Hubbard model on anisotropic triangular lattices, as a continuation of the preceding study [J. Phys. Soc. Jpn 75, 074707 (2006)]. We introduce two new trial states: (i) A coexisting state of (\pi,\pi)-antiferromagnetic (AF) and a d-wave singlet gaps, in which we allow for a band renormalization effect, and (ii) a state with an AF order of 120^\circ spin structure. In both states, a first-order metal-to-insulator transition occurs at smaller U/t than that of the pure d-wave state. In insulating regimes, magnetic orders always exist; an ordinary (\pi,\pi)-AF order survives up to t'/t\sim 0.9 (U/t=12), and a 120^\circ-AF order becomes dominant for t'/t \gsim 0.9. The regimes of the robust superconductor and of the nonmagnetic insulator the preceding study proposed give way to these magnetic domains.Comment: 11 pages, 14 figure

Paramagnetic magnetostriction in the chiral magnet CrNb3S6 at room temperature

We report that the magnetostriction (MS) effects occur in a paramagnetic state of a chiral magnet CrNb3S6. Through a series of experimental tests at room temperature, structural changes were observed at the level of a unit cell. The structural parameters are dependent of the strength and direction of magnetic field (H) even at temperature excessively higher than the magnetic ordering temperature Tc of 127 K. The present paramagnetic MS prominently appeared under H∥ the ab plane (easy plane) as opposed to under H∥ the c axis. Features observed in the paramagnetic MS effect significantly differ from those of the spontaneous MS in the vicinity of Tc [Phys. Rev. B 102, 014446 (2020)]. In this material, the orbital angular momentum L of Cr originates from the hybridization between Cr and Nb, and L is strongly coupled with the crystal structure [Phys. Rev. B 99, 174439 (2019)]. The present study clarified that the symmetry of the CrS6 octahedron is sensitive to H even at room temperature. The paramagnetic spin-orbit coupling should induce the distortion of CrS6 octahedron, resulting in the changes in Cr-Nb(4f) distance via the change in the hybridization between Cr-a1g and Nb-4dz2 orbitals