In this article, we review the history of the development of spin caloritronics and research on various transport phenomena caused by heat-charge-spin current interconversion. We then discuss future prospects in spin caloritronics from the viewpoints of measurement techniques, condensed matter physics, materials science, and engineering applications.

Crystalline polymorphism is a phenomenon in which different crystal structures are formed with the same chemical composition, which is important in materials science and chemical industry. In this study, we investigated the structural changes of NaI and CsCl nanocrystals during the initial stage of crystal growth and the stage of crystal sublimation at the nanoscale by in situ observation on high-speed, high-resolution transmission electron microscopy. We found that polymorphs appearing at the nanoscale differ in stability from the bulk and that a dynamic equilibrium proceeds in less than a second under the influence of the interfacial free energy. As the particles grow, this equilibrium stops and converges to crystalline phases that are either stable or unstable in the bulk, depending on their sizes. These findings open a new avenue for a unified understanding of the thermodynamics and kinetics of crystal growth and reveal the principle behind the principles developed by Ostwald.

We examine the feasibility of the Bell test (i.e., detecting a violation of the Bell inequality) with the ATLAS detector at the Large Hadron Collider (LHC) at CERN through the flavor entanglement between the B mesons. Our simulation studies show that the Bell test is feasible, suggesting the possibility of the Bell test in TeV energy region and may open up a new area for experimental studies of quantum foundations.

We realized feedback cooling of all the mechanical degrees of freedom of a neutral nanoparticle levitated in an optical lattice. Three translational motions are optically cooled to near the ground state, while three librational motions are electrically cooled to below 30 mK. By repeating a release-and-recapture protocol for a specific nanoparticle, we demonstrate time-of-flight measurements of the velocity distribution of a nanoparticle near the ground state and observe widths significantly broader than the values expected with its temperature of the motion. When we apply cooling on all the librational motions, the widths expected from the temperature are recovered. Our observation elucidates coupling between translational and librational motions due to the asymmetric geometry of the nanoparticle.