応用物理学輪講 I
6月14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6月14日（金）16：50～18：50

Aグループ

座長
山口　大輝
指導
教員名
十倉　好紀　卓越教授
発表者名 コラック　尚芸仁平
指導教員名 井手上　敏也　准教授
発表題目（英語） Photocurrent response in geometrically engineered quasi-one-dimensional layered Weyl semimetal ZrTe5
要旨（英語） With van der Waals materials, it is possible to develop physical properties that are not found in homogeneous bulk samples by processing the shape of the thin film sample obtained by cleaving it and fabricating devices. In particular, in recent years, novel physical properties have been reported in geometrically engineered thin film samples, such as voltage response reflecting hydrodynamic transport properties and photocurrent response due to the shape of the sample.
In this study, we fabricate a layered quasi-one-dimensional Weyl semimetal ZrTe5 with strong anisotropy and high mobility into an L-shape, and photocurrent generated by the combination of crystal symmetry and sample geometry was observed. In the presentation, I will report on the dependence of photocurrent on temperature, polarization, shape, etc., and discuss the mechanism.
発表言語 日本語
発表者名 佐々木　猛
指導教員名 長谷川　達生　教授・矢代　航　委嘱教授
発表題目（英語） Research on quantitative thickness extraction from a propagation-based phase contrast image using polychromatic X-rays
要旨（英語） When imaging light-element objects using X-rays, phase contrast information is notable due to weak absorption contrast. Propagation-based method is a way to obtain a phase contrast image as an edge-enhanced image by propagating X-rays refracted by the object in free space. Paganin *et al*. (2002) developed a method to extract the projected thickness of a single-material sample from a propagation-based phase contrast image taken using monochromatic X-rays. This method is known for its robustness even with nonhomogeneous objects and polychromatic illumination, making it useful for high-speed semi-quantitative imaging using polychromatic synchrotron radiation X-rays. In this presentation, I will introduce research on quantitatively deriving the object’s thickness from a propagation-based phase contrast image using white synchrotron X-rays.
発表言語 日本語
発表者名 佐藤　葵
指導教員名 芦原　聡　教授
発表題目（英語） Broadband laser system with Cr:ZnS for driving mid-infrared intra-pulse difference frequency generation　
要旨（英語） The mid-infrared region plays an important role in molecular vibrational spectroscopy. In particular, “molecular fingerprint region” is located at wavelengths above 6.7 μm (corresponding to wavenumber below 1500 cm-1), and we are aiming to develop a broadband coherent light source in this region.
The method we propose is intra-pulse difference frequency generation (IPDFG) with Cr:ZnS mode-locked laser-based broadband light source for drive laser, and wide-gap semiconductor crystals for nonlinear optical crystals. Wide-gap semiconductors (GaSe, ZGP, etc.) are transparent in mid-infrared region, and have higher nonlinearity than oxide crystals (LiNbO3, BaB2O4, etc.). On the other hand, wide-gap semiconductors have smaller bandgap than oxide crystals, and visible and near-infrared ultrashort pulse is unsuitable for IPDFG because of two-photon absorption. Therefore we use Cr:ZnS mode-locked lasers, which have center wavelength of 2.3 um.
In this presentation, we will give details about the broadband, high-power laser system with Cr:ZnS for mid-infrared IPDFG.
発表言語 日本語

Bグループ

座長
結城　賢志
指導
教員名
中村　泰信　教授
発表者名 佐藤　希宏
指導教員名 香取　秀俊　教授
発表題目（英語） Optical cavity to detect atoms
要旨（英語） Optical lattice clocks realizes the measurement of the transition frequency of reference atoms with an accuracy with the 10^ level, enough to be able to measure gravitational potential on a centimeter scale. Furthermore, there's a significant drive for making these clocks portable and perform remote comparisons of gravitational potentials in the context of the prediction of earthquakes. This motivation leads to a new method: Longitudinal Ramsay Spectroscopy, employing the continuous measurement for optical lattice clock. Unlike the current method of intermittent operation, Longitudinal Ramsay Spectroscopy can reduce equipment required. To realize this new method, we explore the new detector that counts the number of atoms involved in optical lattice clocks and generates an error signal to stabilize these atomic clocks. In the Longitudinal Ramsay Spectroscopy, since the spectroscopy process and the atomic numbering process take place simultaneously, the disturbances to the spectroscopy region need to be reduced. Conventional method causes disturbance caused by fluorescence of atoms. Instead, we utilize the phase shift induced by the atoms inside the optical cavity, reducing the disturbance. A design process using ray tracing calculations was conducted, followed by the development of the device and a detailed performance evaluation. In this presentation, we will explain our concept of atom number detection using the optical cavity and share the latest results of our achievements.
発表言語 日本語
発表者名 清水　蓮也
指導教員名 高橋　陽太郎　准教授
発表題目（英語） Observation of magnetic bulk photovoltaic effect in skyrmion-hosting insulator, GaV4S8
要旨（英語） Bulk photovoltaic effect(BPVE) is a second-order nonlinear optical effect which rectifies light into a DC current. The only requirement for BPVE is the breaking of inversion-symmetry(P). However, BPVE is also sensitive to time-reversal symmetry(T) breaking. Therefore, in magnetic systems, we can observe the photocurrent which is related to the breaking of P and T.

In our research, we focus on skyrmion-hosting magnetic Mott insulator, GaV4S8. Below the magnetic ordering temperature, we successfully observed the magnetic BPVE consistent with the magnetic point group of GaV4S8 in the ferromagnetic phase. Furthermore, in the skyrmion phase, there is a possibility to observe a novel BPVE derived from the emergent magnetic field. In this seminar, I will discuss the experimental results of BPVE in GaV4S8.
発表言語 日本語
発表者名 岸本　竜太
指導教員名 小芦　雅斗　教授
発表題目（英語） Better bounds for low-energy product formulas
要旨（英語） Quantum computing is expected to rapidly and efficiently solve a variety of tasks that classical computers are difficult to compute. The simulation of Hamiltonian dynamics in quantum systems is a significant application task, and expected to surpass classical computers in calculation speed.

Prior research has examined the performance of the Hamiltonian dynamics simulation algorithm in general scenarios, without specific initial state conditions. However, the task’s initial state often possesses distinctive structures, such as low-energy states. Little progress has been made in evaluating the performance of the Hamiltonian dynamics simulation algorithm in a low-energy initial state.

In this presentation, based on [1], I will explain the improvements of the Hamiltonian dynamics simulation algorithm based on the product formula, when the initial state is within the low-energy subspace. And I will also discuss the outlook for improving the complexity by assuming physical systems.

[1] arXiv:2402.10362
発表言語 日本語
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