The triangular lattice antiferromagnetic CuFeO₂ has been studied along the path of frustration physics for more than 30 years, and every time there is an innovation in experimental technology or the creation of a new concept of physics in condensed matter field continues to offer new aspects of frustrated magnetism. At present, attempts to create new physical properties by combining the various magnetic orders produced by frustration with other degrees of freedom such as ferroelectricity and crystal lattices are becoming commonplace, but in this review we once again looked back on the development of frustration research, with a focus on CuFeO₂ . I sincerely hope that this paper will be of help to young researchers who are starting to study condensed matter properties related to frustration physics.

Binary colloidal crystals (BCCs), composed of two different sized particles, are highly desired for many applications of colloidal crystals due to their tunable material properties. However, complexity of their structure makes growing BCCs much difficult than growing unary crystals. Based on our detailed observation of the BCCs formation process, we have developed novel growth technique of the BCCs that utilizes heteroepitaxial growth. In this paper, we demonstrate creation of the BCCs using heteroepitaxial growth and successfully create various BCC structures by changing particle size ratios. We found that the particle interaction and lattice spacing of the substrate and the epitaxial layer is found to play important role in the formation of the BCCs. This mechanism is also convinced in the growth of single-component colloidal crystals. We also observed the Frank–van der Merwe (FM), Stranski–Krastanov (SK), and Volmer–Weber (VW) modes, which varied with the lattice-misfit ratio and interparticle interactions between the substrate and epitaxial phase. Colloidal heteroepitaxy has been confirmed as a useful tool for controlling the structure and growth mode, enabling exploration of novel colloidal self-assembly structures.

For a quantum many-body system with a gapped local Hamiltonian, the ground states typically obeys an area law of entanglement. The area law says that for any subregion of the system, the amount of entanglement between the subregion and the rest of the system is bounded by the size of the boundary between them. In this article, we review recent developments of the applications of the area law to a derivation of anyon theory in two-dimensional spin systems.

In the past two decades, studies on chimera states have revealed that partial synchronization is ubiquitous in both artificial and natural oscillatory networks. The importance of partial synchronization has also been recognized in complex oscillatory networks that are deeply associated with our life, including brain neural networks and social networks such as power grids. To investigate such complex systems in terms of synchrony, we introduce a model of partial synchrony by using an analogy of asynchrony to vortices that appear in the two-dimensional XY spin model. The pairwise asynchrony of every two oscillators is discretely quantified by pseudovortices, which provide a graph representation of partial synchrony and an entropic measure of the degree of partiality. For the test of our model and method, we investigate the dynamics of FitzHugh-Nagumo neurons on a complex small-world network. We confirmed that the entropy provides the synchronization phase diagram and the graph representation visualizes the synchronized oscillator dynamics. Our model and method are applicable to the dynamics of general oscillatory networks and will help us visualize and quantify partial synchrony solely from the dynamics data.

For centuries, humans have pondered the origin of matter in the universe. Recent advancements in high-energy accelerators have led to the discovery of key subatomic particles and the development of the Standard Model, which explains many aspects of nature. However, it fails to fully explain phenomena like neutrino properties, dark matter, and the origin of a matter-dominated universe. Recent advancements in quantum science lead to extremely high precision in frequency measurements in atomic and molecular spectra. Observing minute energy shifts in atoms and molecules provides us with an indirect probe of new physics at high-energy scale. For instance, atomic clocks with precision up to 18 digits have been utilized in dark matter search and test of general relativity. Another example is the measurement of electron electric dipole moment using molecules, which now sets constraints on new physics at energy scales of 10 TeV or higher under certain assumptions. To probe even higher energy scales, it is necessary to minimize the measurement errors, especially from the external electric and magnetic fields. A recently proposed approach can significantly reduce these errors while maintaining the high sensitivity to new physics. By selecting an electric field value that equalizes the energy shifts from external electric and magnetic fields in two quantum states, the transition frequency corresponding to the energy difference between these two states becomes unaffected by these external shifts. This opens up possibilities of exploring previously inaccessible high-energy new physics beyond the Standard Model, which could solve mysteries in the fundamental physics.