隠れた対称性の破れを伴う超伝導体におけるトポロジーと強相関効果

付記する学位プログラム名: 京都大学卓越大学院プログラム「先端光・電子デバイス創成学」京都大学新制・課程博士博士(理学)甲第25103号理博第5010号京都大学大学院理学研究科物理学・宇宙物理学専攻(主査)教授 柳瀬 陽一, 教授 石田 憲二, 准教授 北川 俊作学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDGA

Field-induced superconductivity mediated by odd-parity multipole fluctuation

Field-induced superconductivity has long presented a counterintuitive phenomenon and a pivotal challenge in condensed matter physics. In this Letter, we introduce a mechanism for achieving field-induced superconductivity wherein the sublattice degree of freedom and the Coulomb interaction are tightly entwined. Our multipole-resolved analysis elucidates that lifting the fluctuation degeneracy results in an unconventional Cooper pairing channel, thereby realizing field-induced superconductivity. This research substantively augments the exploration of the latent potential of strongly correlated electron systems with sublattice degrees of freedom.Comment: 15 pages (Main text: 9 pages; Supplemental Materials: 6 pages), 5 figures (Main text: 3 figures; Supplemental Materials: 2 figures

Magnetism and superconductivity in mixed-dimensional periodic Anderson model for UTe2_{2}

UTe$_{2}$ is a strong candidate for a topological spin-triplet superconductor, and it is considered that the interplay of magnetic fluctuation and superconductivity is essential for the origin of the superconductivity. Despite various experiments suggesting ferromagnetic criticality, neutron scattering measurements observed only antiferromagnetic fluctuation and called for theories of spin-triplet superconductivity near the antiferromagnetic quantum critical point. We construct a periodic Anderson model with one-dimensional conduction electrons and two- or three-dimensional $f$-electrons, reminiscent of the band structure of UTe$_2$, and show that ferromagnetic and antiferromagnetic fluctuations are reproduced depending on the Fermi surface of $f$ electrons. These magnetic fluctuations cooperatively stabilize spin-triplet $p$-wave superconductivity. We also study hybridization dependence as a possible origin of pressure-induced superconducting phases and find that moderately large hybridization drastically changes the antiferromagnetic wave vector and stabilizes $d$-wave superconductivity.Comment: 6+2 pages, 12 figure

Topological crystalline superconductivity in locally noncentrosymmetric CeRh2_2As2_2

Recent discovery of superconductivity in CeRh$_2$As$_2$ clarified an unusual $H$-$T$ phase diagram with two superconducting phases [Khim et al. arXiv:2101.09522]. The experimental observation has been interpreted based on the even-odd parity transition characteristic of locally noncentrosymmetric superconductors. Indeed, the inversion symmetry is locally broken at the Ce site, and CeRh$_2$As$_2$ molds a new class of exotic superconductors. The low-temperature and high-field superconducting phase is a candidate for the odd-parity pair-density-wave state, suggesting a possibility of topological superconductivity as spin-triplet superconductors are. In this paper, we first derive the formula expressing the $\mathbb{Z}_2$ invariant of glide symmetric and time-reversal symmetry broken superconductors by the number of Fermi surfaces on a glide invariant line. Next, we conduct a first-principles calculation for the electronic structure of CeRh$_2$As$_2$. Combining the results, we show that the field-induced odd-parity superconducting phase of CeRh$_2$As$_2$ is a platform of topological crystalline superconductivity protected by the nonsymmorphic glide symmetry and accompanied by boundary Majorana fermions.Comment: 15 pages (Main text: 7 pages; Supplemental Materials: 8 pages), 8 figures (Main text: 4 figures; Supplemental Materials: 4 figures

CO₂ Emissions from Blade Waste Treatments under Wind Power Scenario in Japan from 2021 to 2100

Nogaki S., Ito L., Nakakubo T., et al. CO₂ Emissions from Blade Waste Treatments under Wind Power Scenario in Japan from 2021 to 2100. Sustainability (Switzerland) 16, 2165 (2024); https://doi.org/10.3390/su16052165.Wind power generation has been introduced to reduce carbon emissions; however, recycling or recovering the waste of wind blades, which contain fibre-reinforced plastic, is difficult. Converting the recovered materials for secondary use is also difficult owing to the decreased strength and low material value. Many countries, including Japan, have not considered the future energy and CO₂ emission scenarios, particularly CO₂ emissions from wind blade waste. Based on these scenarios, Japan has planned to introduce large amounts of onshore/offshore wind power generation through 2050. Therefore, we aimed to evaluate quantitatively the total amount of waste and the global warming potential (GWP) from multiple blade waste treatment processes. Based on the average lifetime of blades (20–25 years), we found that the GWP of wind blade waste treatment in Japan may reach a maximum of 197.3–232.4 MtCO2eq by 2060–2065. Based on this lifetime, the wind blade treatment in 2050 accounted for 63.9–80.1% of the total greenhouse gas emissions in 2050. We also showed that the rise in CO₂ emissions from the wind blade wastes would make up 82.5–93.6% of the potential reduction in the GWP, which is achievable by shifting from thermal to wind power generation

Notch1 and Notch3 Instructively Restrict bFGF-Responsive Multipotent Neural Progenitor Cells to an Astroglial Fate

AbstractNotch1 has been shown to induce glia in the peripheral nervous system. However, it has not been known whether Notch can direct commitment to glia from multipotent progenitors of the central nervous system. Here we present evidence that activated Notch1 and Notch3 promotes the differentiation of astroglia from the rat adult hippocampus-derived multipotent progenitors (AHPs). Quantitative clonal analysis indicates that the action of Notch is likely to be instructive. Transient activation of Notch can direct commitment of AHPs irreversibly to astroglia. Astroglial induction by Notch signaling was shown to be independent of STAT3, which is a key regulatory transcriptional factor when ciliary neurotrophic factor (CNTF) induces astroglia. These data suggest that Notch provides a CNTF-independent instructive signal of astroglia differentiation in CNS multipotent progenitor cells

Multi-scale space-time ansatz for correlation functions of quantum systems

Correlation functions of quantum systems are central objects in quantum field theories which may be defined in high-dimensional space-time domains. The numerical treatment of these objects suffers from the curse of dimensionality, which hinders the application of sophisticated many-body theories to interesting problems. Here, we propose a quantum-inspired Multi-Scale Space-Time Ansatz (MSSTA) for correlation functions of quantum systems. The space-time dependence is mapped to auxiliary qubit degrees of freedom describing exponentially different length scales, and the ansatz assumes a separation of length scales. We numerically verify the ansatz for various equilibrium and nonequilibrium systems and demonstrate compression rates of several orders of magnitude for challenging cases. Essential building blocks of diagrammatic equations, such as convolutions or Fourier transforms are formulated in the compressed form. We numerically demonstrate the stability and efficiency of the proposed methods for the Dyson and Bethe-Salpeter equations. MSSTA provides a unified framework for implementing efficient computations of quantum field theories.Comment: 25 pages, 26 figure