教育活動

2019年4月〜2020年3月 学習院大学物理学科　非常勤講師　（担当講義:　熱学および統計力学２　物３年 （第一学期）　および　熱学および統計力学３　物３年 (第二学期)）
2024年4月〜2024年9月 学習院大学物理学科　非常勤講師　（担当講義:　数学2　物１年 （第一学期））
2020年4月〜2026年3月 学習院大学物理学科　非常勤講師　（担当講義:　物性物理学3　物３年 （第一学期））

研究活動

永井研究室では、人工知能・AI、機械学習を使うことで、これまでにない新しい物理学を開拓することを目的として研究を行なっています。これまで、物理学では物理学者の経験と直観を利用して実験研究および理論研究が進められてきました。そして、計算機の登場により、紙と鉛筆に加えてコンピュータを使う計算物理学と呼ばれる分野が成立しました。そして現在、AI・機械学習の急速な発展により、これらと物理学が融合した新しい分野、「学習物理学」が立ち上がりつつあります。永井研究室は、GPU計算機やマルチコア計算機、そしてスーパーコンピュータなどを駆使して、この新しい分野を切り開こうとしています。

文献

1. Y. Nagai, Y. Kato and N. Hayashi, Analytical Result on Electronic States around a Vortex Core in a Noncentrosymmetric Superconductor, J. Phys. Soc. Jpn. 75 043706-1 043706-4 (2006) DOI: 10.1143/JPSJ.75.043706
2. Y. Nagai, Y. Ueno, Y. Kato and N. Hayashi, Analytical Formulation of the Local Density of States around a Vortex Core in Unconventional Superconductors, J. Phys. Soc. Jpn. 75 104701-1 104701-14 (2006) DOI: 10.1143/JPSJ.75.104701
3. Y. Nagai, Y. Kato, N. Hayashi, K. Yamauchi and H. Harima, Calculated Positions of Point Nodes in the Gap Structure of the Borocarbide Superconductor YNi2B2C, Phys. Rev. B 76, 214514-1 214514-8 (2007) DOI: 10.1103/PhysRevB.76.214514
4. Y. Nagai and N. Hayashi, Kramer-Pesch approximation for analyzing field-angle-resolved measurements made in unconventional superconductors: A calculation of the zero-energy density of states, Phys. Rev. Lett. 101 097001-1 097001-4 (2008) DOI: 10.1103/PhysRevLett.101.097001
5. Y. Nagai, N. Hayashi, N. Nakai, H. Nakamura, M. Okumura and M. Machida, Nuclear magnetic relaxation and superfluid density in Fe-pnictide superconductors: An anisotropic ±s-wave scenario, New J. Phys. 10 103026-1 103026-17 (2008) DOI:10.1088/1367-2630/10/10/103026
6. Y. Nagai and N. Hayashi, Surface Bound States in n-band Systems with Quasiclassical Approach, Phys. Rev. B 79 224508-1 224508-9 (2009) DOI: 10.1103/PhysRevB.79.224508
7. S. Nakakura, Y. Nagai and D. Yoshioka, Uniform current in graphene strip with zigzag edges, J. Phys. Soc. Jpn. 78 065003-1 065003-2 (2009) DOI: 10.1143/JPSJ.78.065003
8. Y. Nagai and Y. Kato, Impurity scattering rate and coherence factor in vortex core of sign-reversing s-wave superconductors, Phys. Rev. B 82 (2010) 174507 DOI: 10.1103/PhysRevB.82.174507
9. N. Nakai, H. Nakamura, Y. Ota, Y. Nagai, N. Hayashi, and M. Machida, First-principles-based ±pm s-wave modeling for iron-based superconductors:Studies for specific heat and nuclear magnetic relaxation rate, Phys. Rev. B 82 094501-1 094501-5 (2010) DOI: 10.1103/PhysRevB.82.094501
10. M. Kunimi, Y. Nagai, and Y. Kato, Josephson effects in one-dimensional supersolids, Phys. Rev. B 84 094521-1 094521-9 (2011) DOI: 10.1103/PhysRevB.84.094521
11. Y. Imai, H. Takahashi, K. Kitagawa, K. Matsubayashi, N. Nakai, Y. Nagai, Y. Uwatoko, M. Machida, A. Maeda, Microwave Surface Impedance Measurements of LiFeAs Single Crystals, J. Phys. Soc. Jpn. 80 013704-1 013704-4 (2011) DOI: 10.1143/JPSJ.80.013704 Most Cited Articles in 2012 from Vol. 80(2011)
12. Y. Nagai, H. Nakamura, and M. Machida, Superconducting Gap Function in an Organic Superconductor (TMTSF)2ClO4 with Anion Ordering; First-principles Calculations and Quasi-classical Analyses for Angle-resolved Heat Capacity, Phys. Rev. B 83 104523-1 104523-8 (2011) DOI: 10.1103/PhysRevB.83.104523
13. Y. Nagai, and K. Kuroki, Determination of the pairing state in iron-based superconductors through neutron scattering, Phys. Rev. B 83 220516-1 220516-4(R) (2011) DOI: 10.1103/PhysRevB.83.220516
14. M. Ishikado, Y. Nagai, K. Kodama, R. Kajimoto, M. Nakamura, Y. Inamura, S. Wakimoto, H. Nakamura, M. Machida, K. Suzuki, H. Usui, K. Kuroki, A. Iyo, H. Eisaki, M. Arai, S. Shamoto, s±-like spin resonance in the iron-based nodal superconductor BaFe2(As0.65P0.35)2 observed using inelastic neutron scattering, Phys. Rev. B 84 144517-1 144517-5 (2011) DOI: 10.1103/PhysRevB.84.144517
15. Y. Nagai, N. Nakai, and M. Machida, Direct Numerical Demonstration of Sign-preserving Quasiparticle Interference via Impurity inside Vortex Core in Unconventional Superconductors, Phys. Rev. B 85 092505-1 092595-4 (2012) DOI: 10.1103/PhysRevB.85.092505
16. Y. Nagai, Y. Ota, and M. Machida, Efficient Numerical Self-consistent Mean-field Approach for Fermionic Many-body Systems by Polynomial Expansion on Spectral Density, J. Phys. Soc. Jpn. 81 024710-1 024710-6 (2012) DOI: 10.1143/JPSJ.81.024710
17. Y. Nagai, and K. Kuroki, Q-scan-analysis of the neutron scattering in iron-based superconductors, Phys. Rev. B 85 134521-1,134521-7 (2012) DOI: 10.1103/PhysRevB.85.134521
18. Y. Nagai, K. Tanaka, and N. Hayashi, Quasiclassical numerical method for mesoscopic superconductors: bound states in a circular d-wave island with a single vortex, Phys. Rev. B 86, 094526-1, 094526-9 (2012) DOI: 10.1103/PhysRevB.86.094526
19. Y. Nagai, H. Nakamura, and M. Machida, Rotational Isotropy Breaking as Proof for Spin-polarized Cooper Pair in Topological Superconductor CuxBi2Se3, Phys. Rev. B 86 094507-1, 094507-5 (2012) DOI:09450710.1103/PhysRevB.86.094507
20. Y. Nagai, Y. Shinohara, Y. Futamura, Y. Ota, and T. Sakurai, Numerical construction of a low-energy effective Hamiltonian in a self-consistent Bogoliubov-de Gennes approach of superconductivity, J. Phys. Soc. Jpn. 82 094701-1,094701-10 (2013) DOI: 10.7566/JPSJ.82.094701
21. Y. Higashi, Y. Nagai, M. Machida, and N. Hayashi, Field-angle resolved flux-flow resistivity as a phase-sensitive probe of unconventional Cooper pairing, Phys. Rev. B 88 224511-1 224511-6 (2013) DOI: 10.1103/PhysRevB.88.224511
22. Y. Nagai, H. Nakamura, and M. Machida, Spin-polarized Majorana Bound States around a Vortex in Topological Superconductors , J. Phys. Soc. Jpn. 83, 064703-1,064703-7 (2014). DOI: 10.7566/JPSJ.83.064703 'Papers of Editors' Choice'
23. Y. Nagai, H. Nakamura, and M. Machida, Quasiclassical Treatment and Odd-parity/Triplet Correspondence in Topological Superconductors, J. Phys. Soc. Jpn. 83 053705-1,053705-4 (2014) DOI: 10.7566/JPSJ.83.053705
24. Y. Nagai, Field-angle-dependent Low-energy Excitations around a Vortex in the Superconducting Topological Insulator CuxBi2Se3, J. Phys. Soc. Jpn. 83 063705-1,063705-4 (2014),DOI: 10.7566/JPSJ.83.063705
25. Y. Nagai, Y. Ota, and M. Machida, Nonmagnetic impurity effects in a three-dimensional topological superconductor: From p- to s-wave behaviors, Phys. Rev. B 89, 214506-1,214506-6 (2014) DOI: 10.1103/PhysRevB.89.214506
26. Y. Nagai, Y. Ota, and M. Machida, Impurity effects in a two-dimensional topological superconductor: A of Tc-robustness with a topological number, J. Phys. Soc. Jpn. 83 094722-1, 094722-5 DOI: 10.7566/JPSJ.83.094722
27. S. Yoshizawa, H. Kim, T. Kawakami, Y. Nagai, T. Nakayama, X. Hu, Y. Hasegawa, and T. Uchihashi, Imaging Josephson vortices on the surface superconductor Si(111)-(√7 x√3)-In using a scanning tunneling microscope, Phys. Rev. Lett. 113, 247004-1,247004-5, DOI: 10.1103/PhysRevLett.113.247004‘Editors' Suggestion’ ’Featured in Physics’
28. Y. Nagai, H. Nakamura, and M. Machida, Surface states around a vortex in topological superconductors: Intersection of a surface and a vortex, J. Phys. Soc. Jpn. 84, 033703-1,033703-4 (2015). DOI: 10.7566/JPSJ.84.033703
29. Y. Nagai, Y. Ota, and M. Machida, Topological s-wave pairing superconductivity with spatial inhomogeneity: Mid-gap-state appearance and robustness of superconductivity, J. Phys. Soc. Jpn. 84, 034711-1,034711-8 (2015). DOI:10.7566/JPSJ.84.034711
30. Y. Nagai,Robust superconductivity with nodes in the superconducting topological insulator CuxBi2Se3: Zeeman orbital field and non-magnetic impurities, Phys. Rev. B 91, 060502(R)-1,060502(R)-5 (2015). DOI: 10.1103/PhysRevB.91.060502
31. A. Shitade and Y. Nagai, Orbital angular momentum in a nonchiral topological superconductor, Phys. Rev. B 92, 024502-1,024502-5 (2015). DOI: 10.1103/PhysRevB.92.024502-7
32. Y. Nagai, H. Nakamura, M. Machida, and K. Kuroki, First-principle study of antimony doping effects on the iron-based superconductor CaFe(SbxAs1-x)2, J. Phys. Soc. Jpn. 84, 093702-1,093702-4 (2015) DOI:10.7566/JPSJ.84.093702
33. Y. Nagai, Y. Ota, and M. Machida, Inverse coherence effects in nuclear magnetic relaxation rates as a sign of topological superconductivity, Phys. Rev. B 92, 180502(R) (2015), 10.1103/PhysRevB.92.180502
34. Y. Higashi, Y. Nagai, T. Yoshida, Y. Masaki, and Y. Yanase, Robust zero-energy bound states around a pair-density-wave vortex core in locally noncentrosymmetric superconductors, Phys. Rev. B 93, 104529 (2016),10.1103/PhysRevB.93.104529
35. A. Shitade and Y. Nagai, Orbital angular momentum in a topological superconductor with Chern number higher than 1, Phys. Rev. B 93, 174517 (2016), DOI:10.1103/PhysRevB.93.174517
36. Y. Nagai and H. Nakamura, Multi-band Eilenberger theory of superconductivity: Systematic low-energy projection, J. Phys. Soc. Jpn. 85, 074707 (2016) DOI: 10.7566/JPSJ.85.074707
37. Y. Nagai, S. Hoshino, and Y. Ota, Critical temperature enhancement of topological superconductors: A dynamical mean-field study, Phys. Rev. B 93, 220505(R) (2016), DOI: 10.1103/PhysRevB.93.220505
38. Y. Nagai, and Y. Ota, Nuclear magnetic relaxation rates of unconventional superconductivity in doped topological insulators, Phys. Rev. B 94, 134516 (2016), DOI: 10.1103/PhysRevB.94.134516
39. Evan D. B. Smith, K. Tanaka, and Y. Nagai, Manifestation of chirality in the vortex lattice in a two-dimensional topological superconductor, Phys. Rev. B 94, 064515 (2016), DOI: 10.1103/PhysRevB.94.064515
40. S. Yonezawa, K. Tajiri, S. Nakata, Y. Nagai, Z. Wang, K. Segawa, Y. Ando, and Y. Maeno, Thermodynamic evidence for nematic superconductivity in CuxBi2Se3, Nature Physics 13, 123 (2017), DOI: 10.1038/nphys3907
41. Y. Nagai, Yasushi Shinohara, Yasunori Futamura, and Tetsuya Sakurai, Reduced-Shifted Conjugate-Gradient Method for a Green's Function: Efficient Numerical Approach in a Nano-structured Superconductor, J. Phys. Soc. Jpn. 86, 014708 (2017), 10.7566/JPSJ.86.014708
42. H. Kim, S.-Z. Lin, M. J. Graf, Y. Miyata, Y. Nagai, T. Kato, and Y. Hasegawa, Electrical Conductivity through a Single Atomic Step Measured with the Proximity-Induced Superconducting Pair Correlation, Phys. Rev. Lett 117, 116802 (2016), DOI:10.1103/PhysRevLett.117.116802
43. Y. Nagai, Y. Ota, and K. Tanaka, Time-reversal symmetry breaking and gapped surface states due to spontaneous emergence of new order in d-wave nanoislands, Phys. Rev. B 96, 060503(R) (2017), DOI: 10.1103/PhysRevB.96.060503
44. S. L. Goertzen, K. Tanaka, and Y. Nagai, Self-consistent study of Abelian and non-Abelian order in a two-dimensional topological superconductor, Phys. Rev. B 95, 064509 (2017), DOI: 10.1103/PhysRevB.95.064509
45. Y. Nagai, H. Shen, Y. Qi, J. Liu, and L. Fu, Self-Learning Monte Carlo Method: Continuous-Time Algorithm, Phys. Rev. B 96, 161102(R) (2017), DOI: 10.1103/PhysRevB.96.161102
46. K. Iida, M. Ishikado, Y. Nagai, H. Yoshida, A. D. Christianson, N. Murai, K. Kawashima, Y. Yoshida, H. Eisaki, and A. Iyo, Spin Resonance in the New-Structure-Type Iron-Based Superconductor CaKFe4As4, J. Phys. Soc. Jpn. 86 093703_1-093703_4 (2017), DOI: 10.7566/JPSJ.86.093703
47. Y. Nagai and H. Shinaoka, Smooth self-energy in the exact-diagonalization-based dynamical mean-field theory: Intermediate-representation filtering approach, J. Phys. Soc. Jpn. 88, 064004 (2019), DOI: 10.7566/JPSJ.88.064004
48. Y. Nagai and Y. Kato, Quasiparticle Bound States around Fractional Vortices in s-wave Superconductor, J. Phys. Soc. Jpn. 88, 054707 (2019), DOI:10.7566/JPSJ.88.054707
49. K. Iida, Y. Nagai, S. Ishida, M. Ishikado, N. Murai, A. D. Christianson, H. Yoshida, Y. Inamura, H. Nakamura, A. Nakao, K. Munakata, D. Kagerbauer, M. Eisterer, K. Kawashima, Y. Yoshida, H. Eisaki, and A. Iyo, Coexisting spin resonance and long-range magnetic order of Eu in EuRbFe4As4, Phys. Rev. B 100, 014506 (2019), DOI: 10.1103/PhysRevB.100.014506
50. M. Kheirkhah, Y. Nagai, C. Chen, F. Marsiglio, Majorana corner flat bands in two-dimensional second-order topological superconductors , Phys. Rev. B 101, 104502 (2020), DOI: 10.1103/PhysRevB.101.104502
51. T. Matsushita, Y. Nagai, S. Fujimoto, Disorder-induced exceptional and hybrid rings in Weyl/Dirac semimetals, Phys. Rev. B 100, 245205 (2019), DOI:10.1103/PhysRevB.100.245205
52. Yuki Nagai, N-independent Localized Krylov Bogoliubov-de Gennes Method: Ultra-fast Numerical Approach to Large-scale Inhomogeneous Superconductors, J. Phys. Soc. Jpn. 89, 074703 (2020)
53. Y. Nagai, M. Okumura, and A. Tanaka, Self-learning Monte Carlo method with Behler-Parrinello neural networks, Phys. Rev. B 101, 115111 (2020), DOI:10.1103/PhysRevB.101.115111
54. Etsuko Itou and Yuki Nagai, Sparse modeling approach to obtaining the shear viscosity from smeared correlation functions, Journal of High Energy Physics volume 2020, 7 (2020)
55. Majid Kheirkhah, Zhongbo Yan, Yuki Nagai, Frank Marsiglio, First and second-order topological superconductivity and temperature-driven topological phase transitions in the extended Hubbard model with spin-orbit coupling, Phys. Rev. Lett. 125, 017001 (2020)
56. Yuki Nagai, Yang Qi, Hiroki Isobe, Vladyslav Kozii, and Liang Fu, DMFT Reveals the Non-Hermitian Topology and Fermi Arcs in Heavy-Fermion Systems, Phys. Rev. Lett. 125, 227204-1, 227204-7 (2020)
57. Yuki Nagai, Masahiko Okumura, Keita Kobayashi, and Motoyuki Shiga, Self-learning hybrid Monte Carlo: A first-principles approach, Phys. Rev. B 102, 041124(R)-1,041124(R)-6 (2020)
58. Hiroshi Shinaoka and Yuki Nagai, Sparse modeling of large-scale quantum impurity models with low symmetries, Physical Review B 103, 045120-1, 045120-8 (2021)
59. Hidehiko Kohshiro, and Yuki Nagai, Effective Ruderman–Kittel–Kasuya–Yosida-like Interaction in Diluted Double-exchange Model: Self-learning Monte Carlo Approach, J. Phys. Soc. Jpn. 90, 034711-1, 034711-8 (2021)
60. Taiki Matsushita, Yuki Nagai, and Satoshi Fujimoto, Spectrum Collapse of Disordered Dirac Landau Levels as Topological Non-Hermitian Physics, J. Phys. Soc. Jpn. 90, 074703-1, 074703-9 (2021)
61. Keita Kobayashi, Yuki Nagai, Mitsuhiro Itakura, and Motoyuki Shiga, Self-learning hybrid Monte Carlo method for isothermal-isobaric ensemble: Application to liquid silica, The Journal of Chemical Physics 155, 034106-1, 034106-9 (2021)
62. Howon Kim, Yuki Nagai, Levente Rózsa, Dominik Schreyer, and Roland Wiesendanger, Anisotropic non-split zero-energy vortex bound states in a conventional superconductor, Applied Physics Reviews 8, 031417-1, 031417-8 (2021)
63. Yuki Nagai, Intrinsic vortex pinning in superconducting quasicrystals, Phys. Rev B 106, 064506-1-10 (2022)
64. Markus Wallerberger, Samuel Badr, Shintaro Hoshino, Sebastian Huber, Fumiya Kakizawa, Takashi Koretsune, Yuki Nagai, Kosuke Nogaki, Takuya Nomoto, Hitoshi Mori, Junya Otsuki, Soshun Ozaki, Thomas Plaikner, Rihito Sakurai, Constanze Vogel, Niklas Witt, Kazuyoshi Yoshimi, Hiroshi Shinaoka, sparse-ir: Optimal compression and sparse sampling of many-body propagators, SoftwareX 21 101266 1-7 (2023)
65. T. Machida, Yuki Nagai, and T. Hanaguri, Zeeman effects on Yu-Shiba-Rusinov states, Phys. Rev. Research 4, 033182 1-12 (2022)
66. Yuki Nagai, Akinori Tanaka, and Akio Tomiya, Self-learning Monte Carlo for non-Abelian gauge theory with dynamical fermions, Phys. Rev. D 107, 054501 1-16 (2023)
67. Yuki Nagai, and Hiroshi Shinaoka, Sparse Modeling Approach for Quasiclassical Theory of Superconductivity, Journal of the Physical Society of Japan 92, 034703 1-8 (2023)
68. Yuki Nagai, Yutaka Iwasaki, Koichi Kitahara, Yoshiki Takagiwa, Kaoru Kimura, Motoyuki Shiga, High-Temperature Atomic Diffusion and Specific Heat in Quasicrystals, Phys. Rev. Lett. 132, 196301 (2024)
69. Yuki Nagai, Akio Tomiya, Self-learning Monte Carlo with equivariant Transformer, J. Phys. Soc. Jpn. 93, 114007 (2024), cond-mat/arXiv:2306.11527
70. Bo Thomsen, Yuki Nagai, Keita Kobayashi, Ikutaro Hamada, Motoyuki Shiga, "Self-learning path integral hybrid Monte Carlo with mixed ab initio and machine learning potentials for modeling nuclear quantum effects in water", J. Chem. Phys. 161, 204109 (2024), arXiv:2411.10122
71. Y. Fujisawa, A. Krishnadas, B. R. M. Smith, M. Pardo-Almanza, H. Hiyane, Y. Nagai, T. Machida, and Y. Okada, "Imaging Josephson Vortices on Curved Junctions", Phys. Rev. B 110, 224511 (2024), http://arxiv.org/abs/2307.11970
72. Yuki Nagai and Akio Tomiya, Gauge covariant neural network for 4 dimensional non-abelian gauge theory, Phys. Rev. D 111, 074501 (2025), hep-lat/arXiv:2103.11965

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