Crystals have ideally well-formed shapes and periodic structure of constituents such as atoms and molecules. Twisting, unusual crystal morphology is one of the poorly understood phenomena of crystals. Continuous twisting structure and crystalline order are such mutually contradicting tendencies. Various mechanisms of crystal twisting have been suggested so far, however, it is still not clear how and why the crystals have spontaneous twisting of the non-long-range translational order. We have recently explored the existence of twisting in high-quality protein crystals by digital X-ray topography. The magnitude of twisting is quite small and cannot be detected by conventional techniques such as optical and electron microscopy. The twisting may be related to the geometric frustration mechanism proposed as a primary mechanism of twisting based on a simulation study. These insights suggest the origin of crystal twisting and methods for controlling crystal perfection.

Superconductivity in d-electron systems, where d electrons of transition metal atoms play an important role in the superconducting properties, has been one of the central issues in condensed matter physics. Recently, more than ten new superconductors with the highest transition temperature T_c of 4.9 K have been discovered in the A₆MX₂ family with hexagonal Zr₆CoAl₂- type crystal structure. We show the physical properties of new superconductors Sc₆MTe₂ and Zr₆MBi₂ containing various transition metal element M. They constitute a unique superconductor family, in which d electrons of 3d, 4d, and 5d M atoms strongly influence the superconducting properties. We hope that the exploration of new superconductors in the A₆MX₂ family will lead to the discovery of new superconductors with higher T_c and unusual superconducting properties.

Waves usually retain their properties during propagation, but in “coherent oscillations,” they can transform into other wave types. This study demonstrates such oscillations between magnons (spin waves) and phonons (sound waves) in ferromagnets using pulsed lasers. Magnons were excited, observed to disappear temporarily, then reappear, indicating their conversion to phonons and back. This dynamic arises from a new eigenstate formed by magnon-phonon interactions, enabling energy exchange before either wave decays.

We are advancing “laser astrophysics” or laboratory plasma astrophysics with high-power lasers. We can produce a high-temperature, high-density, and high-flow-velocity plasma state on a target by focusing a power laser. We want to elucidate the fundamental mechanisms behind astrophysical phenomena by concurrently assessing the global macroscopic structures and local microscopic physical characteristics. Using the Gekko XII laser system at the Institute of Laser Engineering, Osaka University, we promoted laser astrophysics to understand the physics of collisionless shock, turbulent magnetic field amplification, and magnetic reconnection.

We investigated the origin of ferroelectricity and piezoelectricity in BF–BT based ceramics. Despite the pseudo-cubic structure, 0.3BT–0.1BMT–0.6BF ceramics exhibit significant piezoelectric and ferroelectric responses. Analysis of electron density distribution and Rietveld refinement revealed that the Bi ions are off-centered from the corner site of the unit cell. The off-centered Bi ions exhibited partial ordering in the direction of the applied electric field, which is similar to the mechanism of ferroelectric domain switching. The off-centering of Bi ions breaks local symmetry, leading to local spontaneous polarization and the formation of nanodomains. These nanodomains, driven by Bi ion off-centering and partial ordering under applied electric fields, significantly contribute to the extrinsic piezoelectric response. Our findings provide new insights into the role of Bi ion partial ordering and nanodomain behavior under electric field, which are essential for designing Pb-free piezoelectric materials for future applications.