Nuclear cluster dynamics is reviewed from its historical point of view to a new aspect developed recently. After a great success of the model wave function of α-particle condensation is explained, the picture of α condensation is extended to a general concept of nonlocalized clustering, which is applicable to promisingly all the cluster structures. The competition between the localized and nonlocalized cluster motions is discussed in terms of the inter-cluster Pauli repulsion and dynamical character contained in a new wave function proposed recently. It is also shown that the path of cluster evolution, which is indicated by the Ikeda diagram, can be described by the evolution of a “container”, which traps the constituent clusters in a flexible way.
A fascinating hint of cosmic birefringence was observed with 2.4σ statistical significance in polarization data of cosmic microwave background (CMB). Cosmic birefringence refers to the rotation of the polarization plane of the CMB photons. Measurements of cosmic birefringence had been limited by systematic uncertainty on calibrations of polarization sensitive detectors. A novel method mitigated the uncertainty using the polarized Galactic foreground emission as a calibrator. This results in the observation of non-zero cosmic birefringence. It may imply that the parity symmetry is broken in our Universe. Axion-like particle behaving as dark energy can explain the observed cosmic birefringence, if it is coupled to photon. Future CMB observations are expected to shed light on the origin of dark energy.
Recent developments of the theory of crystalline electric field (CEF) and magnetism in the rare-earth based quasicrystals and approximant crystals are overviewed. Magnetic anisotropy arising from the CEF plays a key role in realizing unique magnetic states characterized by the topological charge on the icosahedron. Topological Hall effect is shown to appear under magnetic field accompanied by metamagnetic as well as topological transition in the Tb-based approximants. Ferromagnetic long-range orders have been discovered in the Tb-based quasicrystals.
Producing a large current would typically generate large friction, e.g., Joule heating in electric conduction. In recent years, these kind of aspects have been generalized, and various kinds of trade-off relations between the current and the entropy production have been derived in the field of nonequilibrium statistical mechanics and stochastic thermodynamics. One of the important insight that can be gained from these trade-off relations is that a simultaneous maximization of the thermodynamic efficiency and the output power of heat engines is not possible. While the trade-off relations have been successful in many applications ranging from biomolecular processes to thermoelectric junctions, the effect of quantum coherence was not clear. Here, we have analyzed how coherence affects the trade-off relation between the heat current and the entropy production, and found three general rules summarized as: 1. Coherence between different energy eigenstates makes the trade-off worse, increasing friction. 2. Coherence between degenerate states improves the trade-off, reducing friction. 3. When the amount of coherence between degenerate states is large enough, the trade-off is effectively cancelled and friction virtually vanishes. These findings will contribute to the further understandings between thermodynamic irreversibility and quantum effects, and also open up the possibility to construct a quantum heat engine that effectively attains the Carnot efficiency with finite output power.
A monolayer of transition metal dichalcogenides (TMDs) semiconductors such as MoS2 , MoSe2 , WSe2 , and WS2 had been widely recognized as two-dimensional material and extensively studied for many different applications. In this article, we show that out-of-confinement of wave functions in few-layer TMDs exhibits rich subband quantization phenomena that are totally absent in monolayer crystals. Our finding provides a new direction of utilizing few-layer-thick TMDs to use for subband quantum well devices that bridge the gap between two- and three-dimensional material science.