Surface Bound States in n-band Systems with Quasiclassical Approach

We discuss the tunneling spectroscopy at a surface in multi-band systems such as Fe-based superconductors with the use of the quasiclassical approach. We extend the single-band method by Matsumoto and Shiba [J. Phys. Soc. Jpn. 64, 1703 (1995)] into $n$-band systems ($n \geq 2$). We show that the appearance condition of the zero-bias conductance peak does not depend on details of the pair-potential anisotropy, but it depends on details of the normal state properties in the case of fully-gapped superconductors. The surface density of states in a two-band superconductor is presented as a simplest application. The quasiclassical approach enables us to calculate readily the surface-angular dependence of the tunneling spectroscopy.Comment: 9 pages, 7 figures; References and Discussions update

Multiphase Gas Nature in the Sub-parsec Region of the Active Galactic Nuclei I: Dynamical Structures of Dusty and Dust-free Outflow

We investigated dusty and dust-free gas dynamics for a radiation-driven sub-pc scale outflow in an active galactic nucleus (AGN) associated with a supermassive black hole $10^7 M_\odot$ and bolometric luminosity $10^{44}$ erg s$^{-1}$ based on the two-dimensional radiation-hydrodynamic simulations. A radiation-driven ``lotus-like'' multi-shell outflow is launched from the inner part ($r \lesssim 0.04$ pc) of the geometrically thin disk, and it repeatedly and steadily produces shocks as mass accretion continues through the disk to the center. The shape of the dust sublimation radius is not spherical and depends on the angle ($\theta$) from the disk plane, reflecting the non-spherical radiation field and nonuniform dust-free gas. Moreover, we found that the sublimation radius of $\theta \sim 20$-$60$ deg varies on a timescale of several years. The ``inflow-induced outflow" contributes the obscuration of the nucleus in the sub-parsec region. The column density of the dust-free gas is $N_{\rm H} \gtrsim 10^{22}$ cm$^{-2}$ for $r \lesssim 0.04$ pc. Gases near the disk plane ($\theta \lesssim 30$ degree) can be the origin of the Compton-thick component, which was suggested by the recent X-ray observations of AGNs. The dusty outflow from the sub-parsec region can be also a source of material for the radiation-driven fountain for a larger scale.Comment: 13 pages, 9 figures, accepted for publication in Ap

4D topology optimization: Integrated optimization of the structure and self-actuation of soft bodies for dynamic motions

Topology optimization is a powerful tool utilized in various fields for structural design. However, its application has primarily been restricted to static or passively moving objects, mainly focusing on hard materials with limited deformations and contact capabilities. Designing soft and actively moving objects, such as soft robots equipped with actuators, poses challenges due to simulating dynamics problems involving large deformations and intricate contact interactions. Moreover, the optimal structure depends on the object's motion, necessitating a simultaneous design approach. To address these challenges, we propose "4D topology optimization," an extension of density-based topology optimization that incorporates the time dimension. This enables the simultaneous optimization of both the structure and self-actuation of soft bodies for specific dynamic tasks. Our method utilizes multi-indexed and hierarchized density variables distributed over the spatiotemporal design domain, representing the material layout, actuator layout, and time-varying actuation. These variables are efficiently optimized using gradient-based methods. Forward and backward simulations of soft bodies are done using the material point method, a Lagrangian-Eulerian hybrid approach, implemented on a recent automatic differentiation framework. We present several numerical examples of self-actuating soft body designs aimed at achieving locomotion, posture control, and rotation tasks. The results demonstrate the effectiveness of our method in successfully designing soft bodies with complex structures and biomimetic movements, benefiting from its high degree of design freedom.Comment: 36 pages, 27 figures; for supplementary video, see https://youtu.be/sPY2jcAsNY

Bose-Einstein Condensation of Europium

We report the realization of a Bose-Einstein condensate of europium atoms, which is a strongly dipolar species with unique properties, a highly symmetric $[\mathrm{Xe}]\ 4f^7 6s^2\ {}^8\mathrm{S}_{7/2}$ electronic ground state and a hyperfine structure. By means of evaporative cooling in a crossed optical dipole trap, we produced a condensate of ${}^{151}$Eu containing up to $5\times 10^4$ atoms. The scattering length of ${}^{151}$Eu was estimated to be $a_s = 110(4)\, a_\mathrm{B}$ by comparing the velocities of expansion of condensates with different orientations of the atomic magnetic moments. We observed deformation of the condensate in the vicinity of the Feshbach resonance at $1.32\,\mathrm{G}$ with a width of $10\,\mathrm{mG}$.Comment: 5 pages, 4 figure

Physical properties of portland cement based concrete exposed at a depth of 3520 m in the Nankai Trough

Concrete is widely used in large-scale construction of submarine infrastructure because of its high strength, durability, and ease of handling. However, knowledge of its durability in deep seawater is lacking. In the deep sea, materials are exposed to high pressures and low temperatures, which may cause early deterioration of concrete over time. Concrete materials may also be affected by the chemical composition of seawater, which induces the leaching of calcium. In situ exposure tests are therefore important for understanding degradation processes in the deep sea. In this study, Portland cement based concrete specimens were placed at a depth of 3520 m on the northern edge of the Nankai Trough in 2018 and retrieved in 2019, in the deepest exposure testing conducted to date. Here we provide an outline of the tests, describe the physical properties of materials exposed to deep seawater, freshwater, and air, and discuss possible concrete degradation mechanisms