Tohoku University

About: Tohoku University is a education organization based out in Sendai, Japan. It is known for research contribution in the topics: Magnetization & Population. The organization has 72116 authors who have published 170791 publications receiving 3941714 citations. The organization is also known as: Tōhoku daigaku.

Highly crystalline 2D superconductors

Abstract: Recent advances in materials fabrication have enabled the manufacturing of ordered 2D electron systems, such as heterogeneous interfaces, atomic layers grown by molecular beam epitaxy, exfoliated thin flakes and field-effect devices. These 2D electron systems are highly crystalline, and some of them, despite their single-layer thickness, exhibit a sheet resistance more than an order of magnitude lower than that of conventional amorphous or granular thin films. In this Review, we explore recent developments in the field of highly crystalline 2D superconductors and highlight the unprecedented physical properties of these systems. In particular, we explore the quantum metallic state (or possible metallic ground state), the quantum Griffiths phase observed in out-of-plane magnetic fields and the superconducting state maintained in anomalously large in-plane magnetic fields. These phenomena are examined in the context of weakened disorder and/or broken spatial inversion symmetry. We conclude with a discussion of how these unconventional properties make highly crystalline 2D systems promising platforms for the exploration of new quantum physics and high-temperature superconductors. Highly crystalline 2D superconductors can exhibit very low sheet resistances and unusual physical properties, such as a quantum metallic state, a quantum Griffiths phase and superconductivity robust against in-plane magnetic fields. The origins of these phenomena and the materials in which they are observed are reviewed.

Pressure-induced superconductivity in noncentrosymmetric heavy-fermion CeRhSi3.

Abstract: We report the pressure-induced superconductivity in the noncentrosymmetric heavy-fermion ${\mathrm{CeRhSi}}_{3}$. The superconductivity emerges above about 12 kbar even though the antiferromagnetic ordering persists. Furthermore, another anomaly is observed in the superconducting phase. The anomalous magnetic field-temperature phase diagram with a high upper critical field suggests that an unconventional superconductivity is realized in ${\mathrm{CeRhSi}}_{3}$.

Stellar Abundances for the Galactic Archeology (SAGA) Database — Compilation of the Characteristics of Known Extremely Metal-Poor Stars

Abstract: We describe the construction of a database of extremely metal-poor (EMP) stars in the Galaxy. Our database contains detailed elemental abundances, reported equivalent widths, atmospheric parameters, photometry, and binarity status, compiled from papers in the literature that report on studies of EMP halo stars with [Fe=H] �� 2.5. The compilation procedures for this database were designed to assemble data effectively from electronic tables available from online journals. We have also developed ad ata retrieval system that enables data searches by various criteria and illustrations to explore relationships between stored variables. Currently, our sample includes 1212 unique stars (many of which are studied by more than one group) with more than 15000 individual reported elemental abundances, covering relevant papers published by 2007 December. We discuss the global characteristics of the present database, as revealed by the EMP stars observed to date. For stars with [Fe=H] �� 2.5, the number of giants with reported abundances is larger than that of dwarfs by a factor of two. The fraction of carbon-rich stars (among the sample for which the carbon abundance is reported) amounts to � 30% for [Fe=H] �� 2.5. We find that known binaries exhibit different distributions of the orbital period, according to whether they are giants or dwarfs, and also as a function of the metallicity, although the total sample of such stars is still quite small.