Each year, to recognize significant achievements toward progress in physics, the Physical Society of Japan (JPS) selects outstanding papers from among original research articles published in the Journal of the Physical Society of Japan, Progress of Theoretical Physics, Progress of Theoretical and Experimental Physics, and JPS Conference Proceedings.
The selection committee has chosen the following four papers for the 2022 award based on 16 nominations (15 papers) from editors of the two journals and representatives of the 16 divisions of the JPS.
|Title of Article
|Evolution toward Quantum Critical End Point in UGe2
|J. Phys. Soc. Jpn. 80, 083703 (2011)
|Hisashi Kotegawa , Valentin Taufour, Dai Aoki, Georg Knebel, and Jacques Flouquet
| It has been a new trend to explore novel physical properties around a quantum critical point (QCP) at which an order is tuned to zero by an external parameter. In contrast to the case of antiferromagnetic order, where both theoretical and experimental studies have been devoted, experimental studies of ferromagnetic order are still rare although there are many theoretical approaches. For an itinerant ferromagnetic order, it is known that a second-order phase transition will be taken over by a first-order phase transition, resulting in a new critical end point (CEP) under a magnetic field.
This paper deals with the phase transition in the ferromagnet UGe2 where CEP was not determined, and neither is known for the field- and pressure-dependence of the transition temperature toward CEP. The authors measured the Hall effect and electrical resistivity under various magnetic fields and pressures and subsequently constructed a complete temperature-field-pressure phase diagram. In addition to having exactly determined the CEP, the authors also found that the field- and pressure-dependence of the transition temperature (T_CEP) is not explained by existing theories. They proposed that the details of band structure should be taken into account in theoretical modeling.
The work has become a milestone in the research field and stimulated many later theoretical studies. Therefore, this paper deserves the Outstanding Paper Award from the Physical Society of Japan.
|Title of Article
|Three-Dimensional Dirac Electrons at the Fermi Energy in Cubic Inverse Perovskites: Ca3PbO and Its Family
|J. Phys. Soc. Jpn. 80, 083704 (2011)
|Toshikaze Kariyado and Masao Ogata
| In topological insulators, Dirac electrons with linear dispersion appear only on the surface. In contrast, Dirac semimetals have Dirac points in the bulk electronic state have attracted attention as topologically related materials. This paper is the first paper, from the early days of topological semimetal research, to show through first-principles calculations that the cubic antiperovskite oxide Ca3PbO is a Dirac semimetal. Antiperovskite oxide is an oxide where oxygen is coordinated at the position corresponding to copper in a perovskite structure, and alkali metal (Ca, Sr, etc.) resides at the position of oxygen. Pb (or Sn) takes a rare negative ion valence of −4.
The authors found that in this material system, Dirac electrons appear near the Fermi surface at six symmetric positions around the gamma point due to the band inversion intersection of the d-electron of the alkali metal and the p-electron of Pb (Sn). In addition, the mechanism of the suppression of band repulsion leading to the stable Dirac points without opening a gap due to crystal symmetry is derived from a model for low energy states. Furthermore, the authors discussed the extent of band inversion among a series of antiperovskite oxides.
Following this pioneering work, another group theoretically proposed that some antiperovskite oxides may even become topological crystal insulators. This paper also motivated a number of experimental investigations, including the discovery of superconductivity. In the active research field of topological materials, this paper is considered as a pioneering and highly original paper that triggered progress in international research on Dirac semimetals. For this reason, this paper deserves the Outstanding Paper Award from the Physical Society of Japan.
|Title of Article
|Microscopic Description of Electric and Magnetic Toroidal Multipoles in Hybrid Orbitals
|J. Phys. Soc. Jpn. 87, 033709 (2018)
|Satoru Hayami and Hiroaki Kusunose
| In this paper, the authors derived the quantummechanical operator expressions of new multipoles, i.e., magnetic and electric toroidal multipoles. Electric toroidal multipoles do not appear in the classical electromagnetism framework, but through their understanding of the correspondence between electricity and magnetism, the authors introduced its concept in analogy with magnetic toroidal multipoles.
The authors of the paper also showed that these toroidal moments can be expressed by considering the hybridization between orbitals with different orbital angular momentum, such as p- and d-electrons, and d- and f-electrons. This is an original paper that proposes a microscopic framework for equally treating the magnetic and electric properties of materials and provides a unified basis for arguing physical properties created by multiple degrees of freedom of electrons.
In a later work by the authors [S. Hayami, M. Yatsushiro, Y. Yanagi, and H. Kusunose, Phys. Rev. B 98, 165110 (2018)], together with those by other groups published at the same time, the group-theory based classifications for general multipole ordered phases were provided. The frameworks given in these works are applicable to a variety of realistic materials and emergent cross-correlation responses and led to understanding many important experimental results. This paper played an integral role in the advancement of this discipline and is highly esteemed throughout the community. For these reasons, we determined that this paper deserves the Outstanding Paper Award of the Physical Society of Japan.
|Title of Article
|TeV-scale B − L model with a flat Higgs potential at the Planck scale: In view of the hierarchy problem
|Prog. Theor. Exp. Phys. 2013, 023B08 (2013)
|Satoshi Iso and Yuta Orikasa
| This paper, which is an extension of previous research that realized the electroweak symmetry breaking in the classically conformal model with B-L symmetry, introduces a gauge field for B-L symmetry. The model itself is very simple but contains rich structure. Since there are only two parameters, the model has a high predictive power. In this theory, B-L symmetry breaking and electroweak symmetry breaking by the Coleman-Weinberg mechanism simultaneously take place while solving the gauge hierarchy, and new U (1) gauge bosons and right-handed neutrinos appear in the TeV scale region. Although there are other classically conformal models, this work distinguishes itself in that it is the culmination of the authors' previous research, while being also a pioneering and yet simple and essential model in this field. Another interesting point is that this work provides a new perspective for diverse areas of study, such as neutrino oscillations, inflation, and leptogenesis.
This paper has been cited in many references and has had a significant influence on the development of this field as it is one of the fundamental works in this field. Therefore, we determined that this paper deserves the Outstanding Paper Award of the Physical Society of Japan.