Universal scaling for the spin-electricity conversion on surface states of topological insulators

We have investigated spin-electricity conversion on surface states of bulk-insulating topological insulator (TI) materials using a spin pumping technique. The sample structure is Ni-Fe|Cu|TI trilayers, in which magnetic proximity effects on the TI surfaces are negligibly small owing to the inserted Cu layer. Voltage signals produced by the spin-electricity conversion are clearly observed, and enhanced with decreasing temperature in line with the dominated surface transport at lower temperatures. The efficiency of the spin-electricity conversion is greater for TI samples with higher resistivity of bulk states and longer mean free path of surface states, consistent with the surface spin-electricity conversion

Decay and expansion of the early aftershock activity following the 2011, M_w9.0 Tohoku earthquake

The 2011, M_w9.0 Tohoku earthquake was followed by an abundant amount of seismicity providing a unique opportunity to analyze the triggering mechanism of great earthquakes. Although the Tohoku earthquake occurred close to a dense seismic network, many aftershocks that occurred in the first few hours after the mainshock are not recorded in the earthquake catalogs. Here we use a template waveform approach to recover as many as possible missing events in the first 12 hours following the Tohoku mainshock. Our analysis is able to detect about 1.4 times more events than those listed in the High Sensitivity Seismograph (Hi-net) earthquake catalog. Combining our new dataset with earthquakes that occurred at latter times, we are able to observe a continuous decay of the aftershock rate and along strike expansion of aftershock area. We relate the latter observation to the occurrence of post-seismic slip over the deep interface

Symmetry Breaking for Rho Meson in Neutron Matter

Qualitative changes in the collective excitation spectra of the $\rho$-meson triplet in neutron matter is studied, with particular emphasis on the breaking of the discrete $p\leftrightarrow n$ symmetry. The appearance of additional branches in the dispersion characteristics, the mass splitting among the charge states, the splitting between longitudinal and transverse modes of the $\rho^{\pm}$ mesons and the appearance of `island' modes (or loops) in the time-like region are some of the features that are exposed.Comment: Plain LaTeX fil

Development of a low-mass and high-efficiency charged particle detector

We developed a low-mass and high-efficiency charged particle detector for an experimental study of the rare decay $K_L \rightarrow \pi^0 \nu \bar{\nu}$. The detector is important to suppress the background with charged particles to the level below the signal branching ratio predicted by the Standard Model (O(10$^{-11}$)). The detector consists of two layers of 3-mm-thick plastic scintillators with wavelength shifting fibers embedded and Multi Pixel Photon Counters for readout. We manufactured the counter and evaluated the performance such as light yield, timing resolution, and efficiency. With this design, we achieved the inefficiency per layer against penetrating charged particles to be less than $1.5 \times 10^{-5}$, which satisfies the requirement of the KOTO experiment determined from simulation studies.Comment: 20 pages, 18 figure

Mechanical Properties of Pure Titanium Models Processed by Selective Laser Melting

The influence of laser processing parameters on mechanical properties and microstructure of pure titanium models made by selective laser melting is investigated. The density of the models can reach higher than 95% under proper conditions. Although the tensile strength test shows results comparable to the wrought material, the impact and torsional fatigue strengths are low because of porosity and oxygen pick-up suggested by increasing of hardness. Hot isostatic pressing allows almost full densification and greatly improves mechanical properties.Mechanical Engineerin