Inhomogeneity Effects in Topological Superconductors

We have constructed a quasiclassical framework on superconductors with strong spin-orbit couplings, applicable to CuxBi2Se3[Y. Nagai, H. Nakamura, and M. Machida: arXiv:1305.3025]. The notable point is that in this framework the Bogoliubov-de Gennes Hamiltonians with suggested odd-parity pairing states turn to quasiclassical ones with usual spin-triplet Cooper pairs. Using this quasiclassical theory, we can investigate inhomogeneity effects such as the phenomena with vortices and surfaces in this superconductors and shed light on the pairing state of topological superconductors. In this paper, we apply the quasiclassical framework to the surface bound states with the Dirac-cone energy dispersion originated from the topological invariant in the parent compound Bi2Se3 in order to investigate the robustness of these bound states under the superconducting order parameter. The odd-parity gap functions can not open on the Dirac-cone-dispersion band in the Cu-doped Bi$_{2}$Se$_{3}$ superconductor. We show that the massless Dirac quasiparticles originated from the normal-state topological invariant and the Majorana quasiparticles coexist with each other on the surface in the odd-parity topological superconductivity. Inhomogeneity effects can be easily investigated with the use of our quasiclassical framework in topological superconductors.Comment: 6 pages, 2 figures, submitted to SCES 2013 proceeding

A systemic functional analysis of TOEFL sample writings

The purpose of this study is to investigate the tendency of the structural and lexico-grammatical features between high score writings and low score writings by comparing some sample writings of TOEFL practice text books from the perspectives of Systemic Functional Linguistics. Especially, this study focuses on analyzing clause complex, grammatical metaphor, lexical density, and causality of the sample writings of TOEFL practice books. The analysis shows the tendency to get higher scores with appropriate and effective writing structure of the writing section of TOFL iBT. Actually, most practice textbooks briefly provide only the templates that enable the test takers to memorize the form of the construction of the writing and some simple ways of use of conjunctions which is for logically structured writings. The study proves some defects of introduction and explanation part of the writing section of TOEFL iBT; especially, the explanation of ways of conducting text flow, such as effective use of adverbs and conjunctions and word choices, and so on

Theory for Planar Hall Effect in Organic Dirac Fermion System

In a recent experiment on the interlayer magnetoresistance in the quasi-two-dimensional organic salt, $\alpha$-(BEDT-TTF)$_2$I$_3$, it has been observed that at low temperatures, interlayer tunneling attains phase coherence, leading to the emergence of a three-dimensional electronic structure. Theoretically and experimentally it has been suggested that the system exhibits characteristics of a three-dimensional Dirac semimetal as a consequence of broken time-reversal symmetry and inversion symmetry. Here, we perform a theoretical calculation of the magnetoconductivity under an in-plane magnetic field and demonstrate that the system displays a planar Hall effect. Our calculations are based on a realistic model for $\alpha$-(BEDT-TTF)$_2$I$_3$ incorporating interlayer tunneling and the tilt of the Dirac cone. Given that the planar Hall effect is anticipated as a consequence of chiral anomaly, our findings provide support for the classification of $\alpha$-(BEDT-TTF)$_2$I$_3$ as a three-dimensional Dirac semimetal.Comment: 4 pages, 3 figure

Pressure Effect on the Antiferromagnetic Compound Ce2Ni3Ge5

In this study, the electrical resistivity and magnetization of a single crystal of Ce2Ni3Ge5 heavy fermion compound were performed under pressure. The resistivity and magnetization showed two antiferromagnetic transitions at ambient pressure. On applying pressure, the transitions merged at 1 GPa. At higher pressures, the antiferromagnetic transition temperature decreases, and disappears. It is suggesting that the critical pressure of Ce2Ni3Ge5 was 4.1 GPa