|氏名： 董 禹
指導教員名： 岩佐 義宏 教授
発表題目（英語）： Symmetry engineering in van der Waals interface
要旨（英語）： Van der Waals interface is a unique two dimensional system, which can be made using any combination of van der Waals materials in any sequence . Recently, it is found that two dimensional electronic state realized at the interface can be further tuned by moir? potential or strain [2-4]. Correlated electronic state and superconductivity in twisted heterostructure is one example [2-4]. Another example is the graphene/black phosphorus heterostructure , in which electronic state is affected by the periodic strain and sample-wide quantum transport induced by the strain-induced pseudo-magnetic field has been reported.
To further study the exotic electronic state at a can der Waals interface, we fabricated the graphene/GeS heterostructure, in which GeS has a similar structure like black phosphorus. Quantum transport affected by the periodic potential/strain was observed similarly as in the case of graphene/black phosphorus interface. Detailed gate voltage/magnetic field dependence will be shown in the presentation. Stacking angle dependence and other characteristic features will also be discussed.
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|氏名： 刘 彦慷
指導教員名： 渡辺 悠樹 准教授
発表題目（英語）： Generalized frequency-sum rule on optical conductivity
要旨（英語）：Based on Kubo’s response theory, we studied the optical conductivity of quantum many-body systems in both equilibrium and non-equilibrium and developed a generalization of the frequency-sum rule.
|氏名： 任 統
指導教員名： 為ヶ井 強 准教授
発表題目（英語）： Localmagnetic measurements on topological superconductors
要旨（英語）： Whenthe wave function of a quantum state is intrinsic to a well-defined topologicalnumber, ν, which remains invariant upon adiabatic deformations of the system,it is called a topological state. A certain kind of topological superconductors were found to exhibit very unusual rotational-symmetry breaking in their gapamplitudes. The most famous material to host such a strange phenomenon is thedoped Bi2Se3. They have hexagonallayered structures, whose rotational symmetryin the ab plane is supposed to be a three-fold symmetric, while the measurement on upper critical fields revealedthat it has two-fold symmetry. The magneto-optical (MO) imaging technique, based on the Faraday's effect is an efficient way to capture visuable pictures of magnetization and the possibly existing nematic domain. We may have a deeper look into the origin of the "nematicity" of superconductivity via such local magnetic measurements.
|氏名： WOLSKI Samuel Piotr
指導教員名： 中村 泰信 教授
発表題目（英語）： Quantum magnonics: studying magnons with a superconducting qubit
要旨（英語）： Magnons are the quanta of collective spin excitations in magnetically-ordered materials. Since the late 2000s, there has been a resurgence of interest in magnonics as a promising platform for dissipationless information transport, as well as the potential for transduction of quantum information. Hybrid quantum systems offer a versatile foundation with which to study magnons, as the magnon modes can be coupled to other degrees of freedom and can leverage their complementary properties. I will present recent experiments based on coupling a magnetostatic mode of a ferrimagnetic crystal to a superconducting qubit, introducing nonlinearity into the system and allowing for more complex operations such as magnon-number resolution and quantum sensing of magnons. These experimental demonstrations build towards the ability to create and manipulate of quantum states of magnons, as well as having peripheral applications such as in dark matter detection.
|氏名： XU Tianyu
指導教員名： 小林 洋平 教授
発表題目（英語）： Laser process for superhydrophobic surface formation
要旨（英語）： Superhydrophobic surfaces have attracted increasing attention in recent years due to their wide range of potential industrial applications, including self-cleaning, anti-icing, anticorrosion, etc. The wetting behavior of solid surface is determined by surface roughness and chemical composition, and superhydrophobic surfaces are usually created by fabricating micro-nano structures with surface modification in order to reduce the surface energy.
Laser process, as an efficient method to create rough microstructures on the solid surface, is becoming one of the widely used techniques for superhydrophobic surface formation. However, since the mechanism of laser ablating materials is complex and unexplained, It is hard to find out the best laser parameter for different materials and objectives.
In this presentation, I will present several successed processing samples with superhydrophobic surface including Ti and Cu, and discuss the possibility of deep learning in predicting the laser parameter for superhydrophobic surface processing.
|氏名： 余 同桦
指導教員名： 有田 亮太郎 教授
発表題目（英語）： First-principle material design of functional electrides
要旨（英語）： Electrides are a unique class of ionic solids where interstitial electrons serve as anions. With high conductivity and low work function, anionic electrons exhibit versatile novel functionalities. For instance, magnetic electrides with spin-polarized interstitial states are suitable for spin injection in spintronics. Nevertheless, explorations of properties and applications related to magnetism are limited due to the scarcity of stable magnetic electrides. On another front, recent discoveries have revealed that eletrides are prone to topological phases, which could provide sysmmetry protection for electride devices. Therefore, a systematic structure prediction of magnetic electrides combined with topological properties is urgently needed for future electride application.
In this presentation, I will introduce our design scheme of topological magnectic electrides. To this end, I will explain the primary characteristics of electrides, as well as the crystal structure prediction approach we use. In addition, recent progress will also be presented.