Rendezvous of the Japanese spacecraft Hayabusa with the near-Earth asteroid 25143 Itokawa took place during the interval September through November 2005. The onboard camera imaged the solid surface of this tiny asteroid (535 meters by 294 meters by 209 meters) with a spatial resolution of 70 centimeters per pixel, revealing diverse surface morphologies. Unlike previously explored asteroids, the surface of Itokawa reveals both rough and smooth terrains. Craters generally show unclear morphologies. Numerous boulders on Itokawa's surface suggest a rubble-pile structure.

Dirac semimetals host bulk band-touching Dirac points and a surface Fermi loop. We develop a theory of superconducting Dirac semimetals. Establishing a relation between the Dirac points and the surface Fermi loop, we clarify how the nontrivial topology of Dirac semimetals affects their superconducting state. We note that the unique orbital texture of Dirac points and a structural phase transition of the crystal favor symmetry-protected topological superconductivity with a quartet of surface Majorana fermions. We suggest possible application of our theory to recently discovered superconducting states in Cd3As2.Dirac semimetals are three-dimensional (3D) materials that possess gapless (Dirac) points in the bulk Brillouin zone (BZ), whose low-energy excitations are effectively described as Dirac fermions. With time-reversal symmetry (TRS) and inversion symmetry (IS) preserved, a pair of Dirac points is formed at the crossing of two doubly degenerate bands on a high-symmetry axis. They are protected by discrete rotation (C n ) symmetry [1][2][3][4] [27]. In addition, point contact measurements of Cd 3 As 2 reportedly induce superconductivity around the point contact region, where the tunneling conductance shows a zero-bias conductance peak [23,24]. Au 2 Pb also exhibits a superconducting phase transition after a structural phase transition [26].In this letter we address the effect of the nontrivial topology, i.e., the Dirac points and FL, on the superconducting properties. Topological materials are a promising platform to realize topological superconductors (TSCs) owing to the nontrivial topology of the wave function in normal states [28][29][30][31][32][33]. For instance, surface Dirac fermions may realize a TSC even for an s-wave pairing state [28,29]. Also, the Fermi surface topology, which is the simplest topological structure in the normal state, directly affects the topological superconductivity of oddparity superconductors [30,34]. For the carrier-doped topological insulator, topological superconductivity has been anticipated for the surface [29] or the bulk [30].Here we present a general framework for studying superconductivity in Dirac semimetals. The key ingredients are symmetry-protected topological numbers in crystalline insulators and superconductors [35][36][37][38][39][40][41][42][43][44][45][46]. In particular, we examine the C 4 topological invariant and the mirror Chern number, which ensure the existence of Dirac points and FLs, respectively, in Dirac semimetals. First, we show that these two topological numbers are intrinsically related to each other, establishing a relation between Dirac points and surface FLs. Then, we elucidate how the nontrivial topology of Dirac semimetals affects their superconducting state. We find that for a class of pairing symmetries, Dirac points and FLs in the normal state are inherited as bulk point nodes and surface Majorana fermions (MFs), respectively, in the superconducting state.By carefully examining the low-energy effective Hamiltonian, we also reveal that dope...

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From the group theoretical ground, the Blount's theorem prohibits the existence of line nodes for odd-parity superconductors (SCs) in the presence of spin-orbit coupling (SOC). We study the topological stability of line nodes under inversion symmetry. From the topological point of view, we renovate the stability condition of line nodes, in which we not only generalize the original statement, but also establish the relation to zero-energy surface flat dispersions. The topological instability of line nodes in odd-parity SCs implies not the absence of bulk line nodes but the disappearance of the corresponding zero-energy surface flat dispersions due to surface Rashba SOC, which gives an experimental means to distinguish line nodes in odd-parity SCs from those in other SCs.Comment: 6 pages, 2 figures + 13 pages (supplementary material

Investigations of perovskite oxides triggered by the discovery of high-temperature and unconventional superconductors have had crucial roles in stimulating and guiding the development of modern condensed-matter physics. Antiperovskite oxides are charge-inverted counterpart materials to perovskite oxides, with unusual negative ionic states of a constituent metal. No superconductivity was reported among the antiperovskite oxides so far. Here we present the first superconducting antiperovskite oxide Sr3−xSnO with the transition temperature of around 5 K. Sr3SnO possesses Dirac points in its electronic structure, and we propose from theoretical analysis a possibility of a topological odd-parity superconductivity analogous to the superfluid 3He-B in moderately hole-doped Sr3−xSnO. We envision that this discovery of a new class of oxide superconductors will lead to a rapid progress in physics and chemistry of antiperovskite oxides consisting of unusual metallic anions.

We theoretically study intrinsic superconductivity in doped Dirac semimetals. Dirac semimetals host bulk Dirac points, which are formed by doubly degenerate bands, so the Hamiltonian is described by a $4 \times 4$ matrix and six types of $k$-independent pair potentials are allowed by the Fermi-Dirac statistics. We show that the unique spin-orbit coupling leads to characteristic superconducting gap structures and $d$ vectors on the Fermi surface and the electron-electron interaction between intra and interorbitals gives a novel phase diagram of superconductivity. It is found that when the inter-orbital attraction is dominant, an unconventional superconducting state with point nodes appears. To verify the experimental signature of possible superconducting states, we calculate the temperature dependence of bulk physical properties such as electronic specific heat and spin susceptibility and surface state. In the unconventional superconducting phase, either dispersive or flat Andreev bound states appear between point nodes, which leads to double peaks or single peak in the surface density of states, respectively. As a result, possible superconducting states can be distinguished by combining bulk and surface measurements.Comment: 17 pages, 11 figure

The locations of the pole and rotation axis of asteroid 25143 Itokawa were derived from Asteroid Multiband Imaging Camera data on the Hayabusa spacecraft. The retrograde pole orientation had a right ascension of 90.53 degrees and a declination of -66.30 degrees (52000 equinox) or equivalently 128.5 degrees and -89.66 degrees in ecliptic coordinates with a 3.9 degrees margin of error. The surface area is 0.393 square kilometers, the volume is 0.018378 cubic kilometers with a 5% margin of error, and the three axis lengths are 535 meters by 294 meters by 209 meters. The global Itokawa revealed a boomerang-shaped appearance composed of two distinct parts with partly faceted regions and a constricted ring structure.

Cell surface phosphatidylethanolamine (PE) of the yeast cell was probed by biotinylated Ro09-0198 (Bio-Ro), which specifically binds to PE and was visualized with fluorescein-labelled streptavidin. In Saccharomyces cerevisiae , the signals were observed at the presumptive bud site, the emerging small bud cortex, the bud neck of the late mitotic large-budded cells and the tip of the mating projection. In Schizosaccharomyces pombe , the signals were observed at one end or both ends of mono-nucleated cells and the division plane of the late mitotic cells. These sites were polarized ends in the yeast cells, implying that PE is exposed on the cell surface at cellular polarized ends. Treatment of S. cerevisiae cells with Ro09-0198 resulted in aberrant F-actin accumulation at the above sites, implying that limited surface exposure of PE is involved in the polarized organization of the actin cytoskeleton. Furthermore, S. cerevisiae ros3 , dnf1 and dnf2 null mutants, which were known to be defective in the internalization of fluorescence-labelled PE, as well as the combinatorial mutants, were stained with Bio-Ro at the enlarging bud cortex, in addition to the Bio-Ro-staining sites of wild-type cells, suggesting that Ros3p, Dnf1p and Dnf2p are involved in the retrieval of exposed PE at the bud cortex.