応用物理学輪講 I
6月10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
2022年6月10日（金）16：50～18：50

Aグループ

座長
山本　崇人
指導
教員名
石坂　香子　教授
発表者名 齋藤　真幸
指導教員名 中村　泰信　教授
発表題目（英語） Non-classical correlations between single photons and phonons in an optical fiber
要旨（英語） These days quantum memory has been studied in order to realize quantum communication over long distance, and DLCZ protocol [1] is one of the protocols to realize it. There are many candidates for quantum memory, and the first step to utilize them to quantum memory is observing the violation of Cauchy-Schwarz inequality, which holds about classical field.
The purpose of our research is exploring the possibilities of phonons in an optical fiber for quantum memory. In an optical fiber, the propagating light interacts with phonons and scattering counter-propagating light. This phenomena is called Brillouin scattering, and it has been studied for optical communication. We expect that we can make photon-phonon pairs by weak propagating light, and the phonon can be utilized for quantum memory.
In this presentation, I present our research results of measurement of Brillouin scattering at 10 mK and attempts to observing the violation of Cauchy-Schwarz inequality.

[1] L.-M. Duan et al., Nature 414, 413 (2001)
発表言語 日本語
発表者名 櫻井　快
指導教員名 木村　隆志　准教授
発表題目（英語） Soft X-ray imaging of intracellular structure using ptychography device with Wolter mirror
要旨（英語） Visualizing the intracellular structure and chemical distribution encourages a greater understanding of the functions of cells. Soft X-ray microscopy can identify the chemical states of light-element-rich samples such as cells by absorption spectroscopic technique. In this study, we aim to map the chemical composition of mammalian cells by soft X-ray ptychography, which enables resolution higher than 100 nm. We developed a soft X-ray ptychography system at the synchrotron radiation facility SPring-8. This system is equipped with a cylindrical mirror called Wolter mirror to focus soft X-rays onto the samples. The Wolter mirror without chromatic aberration allows seamless measurements at various energies, including absorption spectroscopy. The compositional distribution of mammalian cells was visualized with a spatial resolution of 50 nm by taking advantage of the characteristics. We expect the system to elucidate the behavior of drugs by observing living cells injected with drugs.
発表言語 日本語
発表者名 末包　海
指導教員名 香取　秀俊　教授
発表題目（英語） Broadband optical frequency comb generation for optical lattice clocks
要旨（英語） Optical lattice clocks are atomic clocks with an uncertainty of 10^-18 and are expected to be applied to relativistic geodesy as gravitational potential meters that can detect height differences of 1 cm. For the application, miniaturization and transportability of optical lattice clocks are required, and this research aims at miniaturization. Lasers used in optical lattice clocks must be frequency-stabilized, and conventionally, cavities and wavelength meters have been used. Therefore, by broadening the spectrum of the optical frequency comb to cover the wavelengths of lasers used in optical lattice clocks, all lasers can be frequency-stabilized into a single optical frequency comb. In this presentation, I will explain the principle of broadband comb generation and the actual spectrum generated using a waveguide PPLN.
発表言語 日本語

Bグループ

座長
米津　和真
指導
教員名
武田　俊太郎　准教授
発表者名 澤村　駿
指導教員名 高橋　陽太郎　准教授
発表題目（英語） Photovoltaic effects by phonon excitation in ferroelectric semiconductor SbSI
要旨（英語） Recently, nonlinear electromagnetics in quantum materials has been studied because it provides the means to probe and control new phase of matter. Above all, "shift current", which can be accounted for in terms of geometric phase, has been attracting much attention. As apposed to the previous photovoltaic effect at the interface, shift current has defect tolerance, and its direction can be reversed by the rotation of the polarization of light. These features lead to new mechanism for generation of electricity.
We focused on a ferroelectric semiconductor SbSI to measure bulk photovoltaic effect by soft phonon excitation under the radiation of terahertz pulses. In this presentation, I will explain the backgrounds of bulk photovoltaic effect including shift current. Then, the property of SbSI and the method of this research are introduced. After that, the results, which indicate large efficiency of the photo current at the resonant frequency, are shown. Finally, future plans for more precise computation of physical quantity are discussed.
発表言語 日本語
発表者名 正力　健太郎
指導教員名 高橋　陽太郎　准教授
発表題目（英語） Magneto-optical response of massive Dirac fermions in kagome magnets
要旨（英語） Light combines with magnetism to produce magneto-optical effects such as the magneto-optical Kerr effect and the Faraday effect. This effect has been applied to technologies such as optical isolators, magnetic domain imaging, and MO disks. Under these circumstances, in the field of material science, the concept of topology, which deals with invariant properties due to continuous deformation, has been attracting attention in recent years, and topological electrons such as Dirac/Weyl fermion have been found in the band structure of k-space.
In recent years, it has been recognized that this Dirac Weyl fermion plays an important role in nonlinear optical responses such as high-order harmonic generation and photocurrent [1]. Topological electronic structure can be regarded as having a magnetic monopole in the k-space, and it is expected that it will be strongly coupled with the magneto-optical response and new charge dynamics will be generated [2].
In this presentation, we will describe the characteristic magneto-optical responses of RMn6Sn6 (R = Tb,Dy), kagome lattice magnets with massive Dirac fermions from lattice geometry.

[1] L. Wu, *et al., *Nat. Phys. 13*,* 350 (2017).
[2] W. K. Tse, & A. H. MacDonald, Phys. Rev. Lett. 105, 057401 (2010).
発表言語 日本語
発表者名 高木　翼
指導教員名 石坂　香子　教授・小川　直毅　委嘱教授
発表題目（英語） Photocurrent spectroscopy in magnetic topological materials
要旨（英語） There are a variety of nonlinear optical(NLO) effects in solid including bulk photovoltaic effect(BPVE), harmonic generations, optical rectification, and nonlinear Kerr rotations. They are typically realized by light irradiation on non-centrosymmetric materials that results in nonlinear polarizations of electron systems. Recent studies have revealed that the topology of the electronic wave function in crystals, especially their phase factors, can describe remarkable physical phenomena such as NLO effects.
Shift current and injection current are known to dominant mechanisms of BPVE. These photocurrents are originated from such phase factors; therefore they could be enhanced in the topological materials with Weyl nodes where Berry curvature diverges. Investigation of relation between photocurrent and phase factors is of great importance in studying topology-related physics as well as for applications in optical devices such as infrared-photodetection sensor or solar cells. In this presentation, result of shift-and injection current spectroscopy on magnetic topological materials, which are (Ge,Mn)Te, MnBi2Te4 are CBST will be given.
発表言語 日本語
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