Tomosuke Aono

Tight-binding theory of surface spin states on bismuth thin films

The surface spin states for bismuth thin films are investigated using an

Micromagnetic analysis of current-induced domain wall motion in a bilayer nanowire with synthetic antiferromagnetic coupling

s{p}^{3}

Influence of classical electromagnetic effects on current-induced domain wall motion in a perpendicularly magnetized nanowire

tight-binding model. The model explains most experimental observations using angle-resolved photoemission spectroscopy, including the Fermi surface, the band structure with Rashba spin splitting, and the quantum confinement in the energy band gap of the surface states. A large out-of-plane spin component also appears. The surface states penetrate inside the film to within approximately a few bilayers near the Brillouin-zone center, whereas they reach the center of the film near the Brillouin-zone boundary.

Conductance and Thermopower of Dirac Fermions under the Kondo Effect

We demonstrate current-induced domain wall motion in bilayer nanowire with synthetic antiferromagnetic(SAF) coupling by modeling two body problems for motion equations of domain wall. The influence of interlayer exchange coupling and magnetostatic interactions on current-induced domain wall motion in SAFnanowires was also investigated. By assuming the rigid wall model for translational motion, the interlayer exchange coupling and the magnetostatic interaction between walls and domains in SAFnanowires enhances domain wall speed without any spin-orbit-torque. The enhancement of domain wall speed was discussed by energy distribution as a function of wall angle configuration in bilayer nanowires.

Numerical Study of Effects of Scattering Processes on Transport Properties of Bi Nanowires

The influence of classical electromagnetic effects such as applied current field and eddy current field on current-induced domain wall motion in a perpendicularly magnetized nanowire was investigated using a micromagnetic framework. The method used to calculate these fields was derived from Maxwell equation in order to estimate the effect of an attached non-magnetic (NM) layer. We demonstrate an applied current field and an eddy current field in a perpendicularly magnetized nanowire with and without a non-magnetic layer. Without a NM layer, the eddy current field causes a small correction in the Gilbert damping with a wall angle dependence. Adding a NM layer enhances the effective Gilbert damping, especially, in terms of wall rotation. Furthermore, an applied current field strongly affects the current-induced domain wall motion, and significantly changes the critical current density and the Walker breakdown.

Numerical Study of Effect of Surface Potential on Transport Properties of Bi Nanowires

We investigate the conductance, thermopower of Dirac fermions through a quantum dot via tunneling barriers described by a pseudogap Anderson model. A sharp peak of the conductance appears when the impurity moment changes abruptly, indicating an impurity quantum phase transition between the Kondo and local moment regimes. In the Kondo regime, the conductance increases as the temperature decreases. The thermopower changes its sign near the Kondo temperature. The Kondo behavior of the pseudogap model is similar to the conventional Kondo problem.