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 2024 award based on 18 nominations (18 papers) from editors of the two journals and representatives of the 16 divisions of the JPS.
| Title of Article | Superconductivity of 2.2 K under Pressure in Helimagnet CrAs |
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| Journal | J. Phys. Soc. Jpn.83,093702(2014) |
| Authors | Hisashi Kotegawa, Shingo Nakahara, Hideki Tou, and Hitoshi Sugawara |
| Citation | Quantum-critical phenomena are one of the central issues in condensed matter physics, and research continues to progress. The authors reported for the first time that by applying relatively low pressure to CrAs, known as a helical magnetic material, a superconducting state appears with the suppression of the magnetic phase. This is the first example of superconductivity observed in a chromium-based material. It is also interesting that superconductivity appears in the vicinity of the helical magnetic phase. This result is based on the successful synthesis of high-quality crystals and the utilization of precise electrical resistance measurements under pressure. The data quality is extremely high and the paper's overall value is even stronger when we consider that this paper introduced a clear pressure-temperature phase diagram. In addition, while similarities in phase diagrams with unconventional superconductors such as iron-based superconductors were demonstrated, this compound has differences in the dimensionality of electronic states between other materials, promoting the subsequent search for new superconducting materials and research on quantum critical phenomena. Indeed, pressure-induced superconductivity has been discovered in chromium- and manganese-based compounds having magnetic structures similar to those of CrAs, Furthermore, new physical properties of CrAs, such as quasilinear quantum magnetoresistance, were revealed. These results are noteworthy in the research of quantum critical phenomena. Therefore, this paper deserves the Outstanding Paper Award from the Physical Society of Japan. |
| Title of Article | Detection of Phase Transition via Convolutional Neural Networks |
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| Journal | J. Phys. Soc. Jpn.86,063001(2017) |
| Authors | Akinori Tanaka and Akio Tomiya |
| Citation |
In recent years, machine learning has often been used in physics research. This paper presented one methodology for detecting phase transition temperatures of statistical mechanical models by machine learning using convolutional neural networks. |
| Title of Article | Topological Hall Effect from Strong to Weak Coupling |
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| Journal | J. Phys. Soc. Jpn.87,033705(2018) |
| Authors | Kazuki Nakazawa, Manuel Bibes, and Hiroshi Kohno |
| Citation | This paper studies the topological Hall effect, which is an electron transport phenomenon in magnetic textures such as magnetic skyrmions. The authors applied a spin gauge field and linear response theory to calculate the Hall effect in wide parameter ranges. In the strong coupling region, the Hall effect is determined by the Berry phase of magnetic textures, as previously understood, but in the weak coupling region, the Berry phase is diluted because of spin diffusion, and the Hall effect differs strongly depending on the parameter region. This paper is important in that it provides a unified theoretical description that covers weak to strong coupling regimes. The results are not only greatly helpful for the interpretation of experiments but also deepen our understanding of the phenomenon. This is an outstanding achievement that deserves the Outstanding Paper Award of the Physical Society of Japan. |
| Title of Article | Unique Helical Magnetic Order and Field-Induced Phase in Trillium Lattice Antiferromagnet EuPtSi |
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| Journal | J. Phys. Soc. Jpn.88.013702(2019) |
| Authors | Koji Kaneko, Matthias D. Frontzek, Masaaki Matsuda, Akiko Nakao, Koji Munakata, Takashi Ohhara, Masashi Kakihana, Yoshinori Haga, Masato Hedo, Takao Nakama, and Yoshichika Ōnuki |
| Citation |
This paper presents the antiferromagnetic order and field-induced magnetic structure in the rare-earth intermetallic compound EuPtSi, which possesses an urmanite-type structure. These characteristics were revealed through single-crystal neutron diffraction. Additionally, this study reports the discovery of an order that corresponds to a magnetic skyrmion lattice. Magnetic skyrmions are vortex-like aggregates of spins, known for their topologically protected stability. This stability has led to their use in innovative magnetic storage devices. In 2009, a triple-q structure on a two-dimensional triangular lattice was observed in the chiral 3d electron system of MnSi. This structure demonstrated the topological Hall effect and garnered significant attention. Following this discovery, similar phenomena were observed in other 3d-electron compounds, leading to research focused on practical applications. However, in 2018, an unusual anomalous Hall effect was reported in the antiferromagnet EuPtSi. This finding hinted at the potential for the first magnetic skyrmion lattice in a 4f electron system. Due to the lack of microscopic observations, further verification of this phenomenon was necessary. This paper details a microscopic study that combines various neutron diffraction techniques to investigate magnetic structures. A key finding is the significant difference in the size of the magnetic skyrmion lattices between MnSi and EuPtSi. In MnSi, the diameter of the lattice is approximately 180 Å, while in EuPtSi, it is markedly smaller, around 18 Å, an order of magnitude less. This smaller size in EuPtSi is noteworthy as it suggests a larger emergent magnetic field due to the magnetic skyrmions, which could lead to a greater topological Hall effect. Indeed, an increase in the topological Hall effect has been observed in EuPtSi. This study is particularly groundbreaking as it is the first to microscopically capture magnetic skyrmion lattices in rare-earth compounds. It provides vital insights into the formation mechanisms and complex physical properties of these lattices. The paper's contributions to the field, especially in guiding subsequent explorations and theoretical studies of magnetic skyrmion lattices in rare-earth compounds, are significant. It is due to these substantial contributions that this paper is deemed an outstanding accomplishment and is deserving of the JPSJ Best Paper Award. |
| Title of Article | Non-invertible topological defects in 4-dimensional ℤ2 pure lattice gauge theory |
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| Journal | Prog. Theor. Exp. Phys. 2022, 013B03 |
| Authors | Masataka Koide, Yuta Nagoya, and Satoshi Yamaguchi |
| Citation | The generalization of the notion of symmetry in quantum field theory has been studied from various angles in recent years. In particular, the importance of expressing generalized symmetries in terms of topological defects has been realized, and at the same time the existence of 'non-invertible symmetries', which, unlike the case of groups, do not have inverse elements, has become apparent. In this paper, by extending the method of topological defects in the two-dimensional Ising model with Kramers-Wannier duality and Z2 symmetry, concrete examples of topological defects and non-invertible symmetry in four dimensions are given constructively for the first time. Specifically, in a four-dimensional Z2 lattice gauge theory with Kramers-Wannier-Wegner duality and 1-form Z2 symmetry, the topological defects associated with this duality and symmetry are derived, and their commutation relations and the existence of non-invertible symmetry are explicitly given. This paper is recognized as an achievement worthy of the Outstanding Paper Award of the Physical Society of Japan, as it has triggered a significant acceleration in the study of non-invertible symmetries in four-dimensional field theories with duality. |