応用物理学輪講 I
10月4日
[注意事項]
発表の10日前までに　office[at]ap.t.u-tokyo.ac.jp　宛てに「氏名」「指導教員」「発表題目（英語）」「要旨（英語）」「発表言語（英語または日本語）」を送付して下さい。
発表日
2024年10月4日（金）16：50～18：50

Aグループ

座長
吉冨　成哉
指導
教員名
求　幸年　教授
座長
井上　裕貴
指導
教員名
関　真一郎　准教授
発表者名 姜　大模
指導教員名 森本　高裕　准教授
発表題目（英語） Ginzburg-Landau simulations of a superconductor illuminated by optical vortex beam.
要旨（英語） Light with orbital angular momentum (LOAM), so-called optical vortex beam was first introduced in 1992 by Allen et al. [1], making a significant advancement in optical technology. The unique structure and tunability of vortex beams have since led to extensive research into various applications, including quantum computation, optical manipulation, and optical communication [2]. Despite these developments, the interaction of LOAM and matter remains not fully understood. This gap is largely attributed to the mismatch between the energy scale and the spatial structure of optical vortices which generates the orbital angular momentum of light.

In this presentation, I will explain the concept of LOAM and the recent studies on the interaction between LOAM and matter. Following this, I will present my latest results from Ginzburg-Landau simulations of a superconductor illuminated by optical vortex beam.

[1] L. Allen et al., Phys. Rev. A *45*, 8185 (1992).
[2] Y. Shen et al., Light Sci Appl *8*, 90 (2019).
発表言語 英語
発表者名 和田島　周星
指導教員名 求　幸年　教授
発表題目（英語） Spin glass vs. SYK-like chaos in a randomly-coupled Pauli spins model
要旨（英語） Spin glasses are formed through disordered and frustrated interactions, and in infinite-range randomly-coupled models like the Sherrington-Kirkpatrick (SK) model, a transition to the spin glass phase occurs at a low temperature. On the other hand, the Sachdev-Ye-Kitaev (SYK) model, an infinite-range model involving Majorana fermions, has gained attention for its quantum chaotic properties, serving as a framework to study phenomena such as information scrambling and strange metals. In this presentation, I will introduce an SYK-like spin model, in which the Majorana fermion operators in the SYK model are replaced by Pauli spin operators. I discuss the competition between the spin glass state, which features characteristics of the SK model, and the chaotic state, reminiscent of the SYK model, and how this competition reveals new insights into disorder and frustration in spin systems.
発表言語 日本語
発表者名 渡邊　瀬名
指導教員名 渡辺　悠樹　准教授
発表題目（英語） Gauge-invariant electromagnetic responses in superconductors
要旨（英語） In recent years, the optical response of superconductors has become a subject of research. However, the theoretical treatment of the electromagnetic response in superconductors requires specific attention.
This is because superconductors exist in a state where the U(1) gauge symmetry is spontaneously broken.

The approach to overcome such a challenge has been addressed within the framework of linear response by Nambu [1]. It is known that applying "vertex corrections" to ordinary Kubo's formula can resolve that issue.

In this presentation, we discuss extending this method to nonlinear responses as a treatment of more general many-body problems. Furthermore, we will show that the electromagnetic response of BCS superconductors can be discussed gauge-invariantly within the framework of the general theory of many-body systems.

[1] Y. Nambu, Phys. Rev. *117*, 648-663 (1960).
発表言語 日本語

Bグループ

座長
大村　洸翔　
指導
教員名
志村　努　教授
座長
岡崎　淳哉
指導
教員名
長谷川　幸雄　教授
発表者名 ZAINUDIN Redza
指導教員名 中村　泰信　教授
発表題目（英語） Photon emission in fluxonium via an electron shelving mechanism
要旨（英語） Reliable quantum state transfer protocols are needed to realize many goals in quantum computing, such as long distance quantum communication and distributed quantum computer systems. A building block of quantum state transfers are photon emissions from qubits, as this allows quantum information to be carried over longer distances compared to static qubits.
Here, a novel photon emission method using fluxonium qubits will be presented, and its working mechanisms will be discussed.
発表言語 英語
発表者名 BAEK　Gwangil
指導教員名 平山　元昭　特任准教授
発表題目（英語） Research on current-induced orbital magnetisation
要旨（英語） The coupling of magnetic and electric effects in materials has led to significant advancements in both theoretical physics and industrial applications. The magnetoelectric effect, which gave rise to new physics fields such as spintronics and multiferroics, requires heavy atoms with strong spin-orbit interaction for its industrial applications. Recently, a new current-induced effect called the Orbital Edelstein effect has been proposed, which does not require spin-orbit interaction for magnetisation, as well as modern construction of the orbital magnetization theory.
In this presentation, we will introduce the following concepts based on these theories: (1) a brief overview of the Orbital Edelstein effect, (2) Exploration of materials exhibiting the maximum current-induced orbital magnetization response using ab-initio methods. (3) Future research plans, including the investigation of mechanisms in light elements.
発表言語 日本語
発表者名 青柳　俊吾
指導教員名 金澤　直也　准教授
発表題目（英語） Nonreciprocal Responses in Optics and Electrical Conduction
要旨（英語） In recent years, nonreciprocal responses arising from chirality, particularly nonreciprocal conduction, have been attracting significant attention in the context of potential applications to electronics and spintronics. Conversely, nonreciprocal optical responses such as magneto-chiral dichroism in the realm of optics have long been recognized and observed not only in ferromagnetic materials and chiral substances under external magnetic fields but also in materials exhibiting antiferromagnetism. The phenomena in these two research areas fundamentally originate from the same symmetry principles, suggesting the possibility of discussing them within a unified theoretical framework. In this presentation, we will introduce experimental examples from both subject areas and explore the similarities between them.
発表言語 日本語
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