2023年度 前期 物理学教室コロキウム
【講演者】Michael E. Peskin (SLAC, Stanford University, Professor)
「What Is the Next Milestone for High-Energy Particle Colliders?」
April 7, 17:00-18:30
Department colloquium by Michael E. Peskin
（SLAC, Stanford University, Professor)
The CERN Large Hadron Collider (LHC) has discovered the Higgs boson and confirmed the predictions for many of its properties given by the “Standard Model” of particle physics. However, this does not mean that particle physics is solved. Mysteries that the Standard Model does not address are still with us and, indeed, stand out more sharply than ever. To understand these mysteries, we need experiments at still higher energies. In this colloquium, I will argue that we should be planning for a particle collider reaching energies of about 10 times those of the LHC in the collisions of elementary particles. Today, there is no technology that can produce such energies robustly and at a reasonable cost. However, many solutions are under study, including colliders for protons, muons, electrons, and photons. I will review the status of these approaches to the design of the next great energy-frontier accelerator.
(Department of Physics and Astronomy Johns Hopkins University, Professor)
「Half Quantum Flux in Spin Triplet Superconductors」
May 19, 17:00-18:30
Department colloquium by Chia-Ling Chien.
（Department of Physics and Astronomy Johns Hopkins University, Professor)
The overwhelming majority of superconductors (SCs) are spin singlet SCs, mostly s-wave (e.g., Nb, MgB2, Fe pnictides) and some d-wave (high TC cuprates). Spin triplet SCs are elusive and difficult to identify. Large upper critical field (HC2) and NMR Knight shift have been employed with Sr2RuO4 as a noted disappointment.
We instead use phase-sensitive method of half-quantum flux (HQF) to identify triplet SCs, which have odd-parity gaps as opposed to the even-parity gaps in singlet SCs. We have observed HQF of (n + ½)Fo, where Fo = hc/2e is the flux quantum and n an integer, in sub-µm rings of spin triplet -Bi2Pd , whereas integer flux nFo has been universally observed in singlet SC rings. Noncentrosymmetric SCs with an admixture of spin triplet pairing also exhibit HQF . Very recently, we show composite rings of two SCs, first proposed by byGeshkenbein, Larkin, and Barone , can unequivocally identity any SC, singlet or triplet. Spin triplet SCs, crucial for Majorana physics and fault tolerant quantum computing, may be exploited in flux qubits.
 Yufan Li, Xiaoying Xu, M. H. Lee, M. W. Chu, and C. L. Chien, Science, 366, 238 (2019).
 Xiaoying Xu, Yufan Li, and C. L. Chien, Phys. Rev. Lett. 124, 167001 (2020).
 V. B. Geshkenbein, A. I. Larkin, and A. Barone, Phys. Rev. B 36, 235 (1987).
【講演者】玉川 徹 (理化学研究所・開拓研究本部 主任研究員/仁科加速器科学研究センター 室長)
June 16, 17:00-18:30
Department colloquium by Toru Tamagawa.
問い合せ： 東京大学 大学院理学系研究科 物理学専攻事務室