Directory of Researchers
| UEMOTO Mitsuharu |  |
| Graduate School of Engineering / Department of Electrical and Electronic Engineering | |
| Assistant Professor | |
| Physics |
Researcher Profile and Settings
Affiliation
＜Faculty / Graduate School / Others＞
Graduate School of Engineering / Department of Electrical and Electronic Engineering＜Related Faculty / Graduate School / Others＞
Faculty of Engineering / Department of Electrical and Electronic Engineering
Teaching
- Faculty of Engineering / Department of Electrical and Electronic Engineering, 2022, Electrical and Electronics Engineering Laboratory ⅡA
- Faculty of Engineering / Department of Electrical and Electronic Engineering, 2022, Electrical and Electronics Engineering Laboratory ⅡA
- Faculty of Engineering / Department of Electrical and Electronic Engineering, 2022, Electrical and Electronics Engineering Laboratory ⅡB
- Faculty of Engineering / Department of Electrical and Electronic Engineering, 2022, Electrical and Electronics Engineering Laboratory ⅡB
Research Activities
Research Areas
Committee Memberships
Awards
May 2023 一般社団法人HPCIコンソーシアム, HPCIソフトウェア賞(奨励賞), SALMON (Scalable Ab-initio Light-Matter simulator for Optics and Nanoscience)
Oct. 2021 The 5th International Symposium for The Core Research Clusters for Materials Science and Spintronics, and The 4th Symposium on International Joint Graduated Program in Materials Science, Poster Award, Robust interfacial anisotropic orbital moment induced at crystallographically heterogeneous graphene/L10-FePd interface
Sep. 2021 The Japan Society of Applied Physics, Poster Award, Anisotropic orbital moment induced at graphene / L10-alloy hybrid interface
Dec. 2013 第24回光物性研究会, 光物性研究会奨励賞, 半導体ナノギャップ共振器によるラビ分裂の計算
Published Papers
The NV centers in a diamond were successfully created by the femtosecond laser single pulse. We also investigated the effect on the diamond lattice induced by the different laser pulse widths from both experimental and theoretical perspectives. Interestingly, in spite of the high thermal conductivity of a diamond, we found that there is a suitable pulse repetition rate of several tens kHz for the formation of NV center ensembles by the femtosecond laser pulse irradiation.
Optica Publishing Group, 16 Jan. 2023, Optics Express, 31 (2), 1594 - 1594, English[Refereed]
Scientific journal
- Last, Dec. 2022, Proceedings of the 33th Symposium of Association for Condensed Matter Photophysics, 135 - 138, JapaneseFirst-principles simulation of nonlinear optical properties of III-V semiconductors
Research society
We propose the atomic structures of the 4H-SiC/[Formula: see text] interface for [Formula: see text] face (1[Formula: see text]00), [Formula: see text] face (11[Formula: see text]0), the C face (000[Formula: see text]), and Si face (0001) after NO annealing using the OH-terminated SiC surface models. Our proposed structures preferentially form at the topmost layers of the SiC side of the interface, which agrees with the experimental finding of secondary-ion mass spectrometry; that is, the N atoms accumulate at the interface. In addition, the areal N-atom density is of the order of [Formula: see text] for each plane, which is also consistent with the experimental result. Moreover, the electronic structure on the interface after NO annealing in which the CO bonds are removed and the nitride layer only at the interface is inserted, is free from gap states, although some interface models before NO annealing include the gap states arising from the CO bonds near the valence band edge of the bandgap. Our results imply that NO annealing can contribute to the reduction in the density of interface defects by forming the nitride layer.
AIP Publishing, 21 Oct. 2022, Journal of Applied Physics, 132 (15), 155701 - 155701, English[Refereed]
Scientific journal
Graphene on [Formula: see text]-FePd(001), which has been experimentally studied in recent years, is a heterogeneous interface with a significant lattice symmetry mismatch between the honeycomb structure of graphene and tetragonal alloy surface. In this work, we report on the density functional study of its atomic-scale configurations, electronic and magnetic properties, and adsorption mechanism, which have not been well understood in previous experimental studies. We propose various atomic-scale models, including simple nontwisted and low-strain twisted interfaces, and analyze their energetical stability by performing structural optimizations using the van der Waals interactions of both DFT-D2 and optB86b-vdW functionals. The binding energy of the most stable structure reached [Formula: see text] eV/atom for DFT-D2 ([Formula: see text] eV/atom for optB86b-vdW). The calculated FePd-graphene spacing distance was approximately 2 Å, which successfully reproduced the experimental value. We also find out characteristic behaviors: the modulation of [Formula: see text]-bands, the suppression of the site-dependence of adsorption energy, and the rise of moiré-like corrugated buckling. In addition, our atomic structure is expected to help build low-cost computational models for investigating the physical properties of [Formula: see text] alloys/two-dimensional interfaces.
AIP Publishing, 07 Sep. 2022, Journal of Applied Physics, 132 (9), 095301 - 095301, English[Refereed]
Scientific journal
We have developed a computational method to describe the nonlinear light propagation of an intense and ultrashort pulse at oblique incidence on a flat surface. In the method, coupled equations of macroscopic light propagation and microscopic electron dynamics are simultaneously solved using a multiscale modeling. The microscopic electronic motion is described by first-principles time-dependent density functional theory. The macroscopic Maxwell equations that describe oblique light propagation are transformed into one-dimensional wave equations. As an illustration of the method, light propagation at oblique incidence on a silicon thin film is presented.
Optica Publishing Group, 20 Jun. 2022, Optics Express, 30 (13), 23664 - 23664, English[Refereed]
Scientific journal
Abstract The stability and formation mechanism of the defects relevant to silicon and carbon vacancies at the 4H-SiC($000\bar{1}$)/SiO2 interface after wet oxidation are investigated by first-principles calculation based on the density functional theory. The difference in the total energy of the defects agrees with the experimental results concerning the density of defects. We found that the characteristic behaviors of the generation of defects are explained by the positions of vacancies and antisites in the SiC($000\bar{1}$) substrate and that the formation of silicon and carbon vacancies is relevant to the generation mechanism of defects. The generation of silicon and carbon vacancies is attributed to the termination of dangling bonds by H atoms introduced by wet oxidation, resulting in the generation of carbon-antisite–carbon-vacancy and divacancies defects in wet oxidation.
IOP Publishing, 25 Mar. 2022, Japanese Journal of Applied Physics, 61 (SH), SH1001 - SH1001, English[Refereed]
Scientific journal
A crystallographically heterogeneous interface was fabricated by growing hexagonal graphene (Gr) using chemical vapor deposition (CVD) on a tetragonal FePd epitaxial film grown by magnetron sputtering. FePd was alternately arranged with Fe and Pd in the vertical direction, and the outermost surface atom was identified primarily as Fe rather than Pd. This means that FePd has a high degree of L10-ordering, and the outermost Fe bonds to the carbon of Gr at the interface. When Gr is grown by CVD, the crystal orientation of hexagonal Gr toward tetragonal L10-FePd selects an energetically stable structure based on the van der Waals (vdW) force. The atomic relationship of Gr/L10-FePd, which is an energetically stable interface, was unveiled theoretically and experimentally. The Gr armchair axis was parallel to FePd [100]L10, where Gr was under a small strain by chemical bonding. Focusing on the interatomic distance between the Gr and FePd layers, the distance was theoretically and experimentally determined to be approximately 0.2 nm. This shorter distance (≈0.2 nm) can be explained by the chemisorption-type vdW force of strong orbital hybridization, rather than the longer distance (≈0.38 nm) of the physisorption-type vdW force. Notably, depth-resolved X-ray magnetic circular dichroism analyses revealed that the orbital magnetic moment (Ml) of Fe in FePd emerged at the Gr/FePd interface (@inner FePd: Ml = 0.16 μB → @Gr/FePd interface: Ml = 0.32 μB). This interfacially enhanced Ml showed obvious anisotropy in the perpendicular direction, which contributed to interfacial perpendicular magnetic anisotropy (IPMA). Moreover, the interfacially enhanced Ml and interfacially enhanced electron density exhibited robustness. It is considered that the shortening of the interatomic distance produces a robust high electron density at the interface, resulting in a chemisorption-type vdW force and orbital hybridization. Eventually, the robust interfacial anisotropic Ml emerged at the crystallographically heterogeneous Gr/L10-FePd interface. From a practical viewpoint, IPMA is useful because it can be incorporated into the large bulk perpendicular magnetic anisotropy (PMA) of L10-FePd. A micromagnetic simulation assuming both PMA and IPMA predicted that perpendicularly magnetized magnetic tunnel junctions (p-MTJs) using Gr/L10-FePd could realize 10-year data retention in a small recording layer with a circular diameter and thickness of 10 and 2 nm, respectively. We unveiled the energetically stable atomic structure in the crystallographically heterogeneous interface, discovered the emergence of the robust IPMA, and predicted that the Gr/L10-FePd p-MTJ is significant for high-density X nm generation magnetic random-access memory (MRAM) applications.
American Chemical Society (ACS), 22 Mar. 2022, ACS Nano, 16 (3), 4139 - 4151, English, International magazine[Refereed]
Scientific journal
In the field of optical science, it is becoming increasingly important to observe and manipulate matter at the atomic scale using ultrashort pulsed light. For the first time, we have performed the ab initio simulation solving the Maxwell equation for light electromagnetic fields, the time-dependent Kohn-Sham equation for electrons, and the Newton equation for ions in extended systems. In the simulation, the most time-consuming parts were stencil and nonlocal pseudopotential operations on the electron orbitals as well as fast Fourier transforms for the electron density. Code optimization was thoroughly performed on the Fujitsu A64FX processor to achieve the highest performance. A simulation of amorphous SiO2 thin film composed of more than 10,000 atoms was performed using 27,648 nodes of the Fugaku supercomputer. The simulation achieved excellent time-to-solution with the performance close to the maximum possible value in view of the memory bandwidth bound, as well as excellent weak scalability.
SAGE Publications, 02 Jan. 2022, The International Journal of High Performance Computing Applications, 36 (2), 182 - 197, English[Refereed]
Scientific journal
A nitridation annealing process is well employed to reduce interface trap states that degrade the channel mobility of 4H-SiC/SiO${}_2$ metal-oxide-semiconductor field-effect transistor. In recent experiments, the existence of high N-atom density layers at the annealed interface is reported and their concentrations are known to be anisotropic in the crystal planes. Until now, the role of atomic structure and the electronic states surrounding the N atoms incorporated by the nitridation annealing process on the origin of anisotropy is not well understood. In this work, we propose a simplified atomic-scale model structure of 4H-SiC with the a high N-atom density layer ($\sim 10^{15}~\mathrm{atom}/\mathrm{cm}^2$), which is of the order of the experimental observation. We use bulk 4H-SiC as host crystal and consider several sets of the atomic configurations of the N-atom incorporated structure at the cubic ($k$) and hexagonal ($h$) sites on $a$-, $m$-, and Si- (C-) planes. Based on the density functional theory calculations, we investigate the influence of the energy stability on the distribution directions. Although our bulk model is simplified compared to the realistic interface structures, we confirm significant difference among models and observe that the incorporation of N atoms on the $a$-face is stable. Furthermore, from the analysis of the electronic states, we suggest that this anisotropy of the formation energy originates from the change of the coordinating number due to the difference in geometric configurations of the N-atom incorporated structures.
Physical Society of Japan, 15 Dec. 2021, Journal of the Physical Society of Japan, 90 (12), English[Refereed]
Scientific journal
- Last, Dec. 2021, Proceedings of the 32th Symposium of Association for Condensed Matter Photophysics, 75 - 78, JapaneseFirst-principles study of ultrafast saturable absorption of 2D transition metal dichalcogenide monolayers
Symposium
Recent developments in attosecond technology led to table-top x-ray spectroscopy in the soft x-ray range, thus uniting the element- and state-specificity of core-level x-ray absorption spectroscopy with the time resolution to follow electronic dynamics in real-time. We describe recent work in attosecond technology and investigations into materials such as Si, SiO2, GaN, Al2O3, Ti, and TiO2, enabled by the convergence of these two capabilities. We showcase the state-of-the-art on isolated attosecond soft x-ray pulses for x-ray absorption near-edge spectroscopy to observe the 3d-state dynamics of the semi-metal TiS2 with attosecond resolution at the Ti L-edge (460 eV). We describe how the element- and state-specificity at the transition metal L-edge of the quantum material allows us to unambiguously identify how and where the optical field influences charge carriers. This precision elucidates that the Ti:3d conduction band states are efficiently photo-doped to a density of 1.9 x 10(21) cm(-3). The light-field induces coherent motion of intra-band carriers across 38% of the first Brillouin zone. Lastly, we describe the prospects with such unambiguous real-time observation of carrier dynamics in specific bonding or anti-bonding states and speculate that such capability will bring unprecedented opportunities toward an engineered approach for designer materials with pre-defined properties and efficiency. Examples are composites of semiconductors and insulators like Si, Ge, SiO2, GaN, BN, and quantum materials like graphene, transition metal dichalcogens, or high-Tc superconductors like NbN or LaBaCuO. Exiting are prospects to scrutinize canonical questions in multi-body physics, such as whether the electrons or lattice trigger phase transitions.
AMER INST PHYSICS, Mar. 2021, APPLIED PHYSICS REVIEWS, 8 (1), English[Refereed]
Scientific journal
We theoretically investigate ultrafast and nonlinear optical properties of graphite thin films based on firstprinciples time-dependent density functional theory. We first calculate electron dynamics in a unit cell of graphite under a strong pulsed electric field and explore the transient optical properties of graphite. The optical response of graphite shows a sudden change from the conducting to the insulating phase at a certain intensity range of the applied electric field. It also appears to be a saturable absorption (SA) in the energy transfer from the electric field to electrons. We next investigate a light propagation in graphite thin films by solving the coupled dynamics of the electrons and the electromagnetic fields simultaneously. It is observed that the SA manifests in the propagation with small attenuation in the spatial region where the electric field amplitude is about 4 x 10(-2) to 7 x 10(-2) V/A.
American Physical Society (APS), 23 Feb. 2021, Physical Review B, 103 (8), English[Refereed]
Scientific journal
- IEEE, Oct. 2019, 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), EnglishAttosecond Soft-X-Ray Spectroscopy in a Transition Metal Dichalcogenide
International conference proceedings
We propose a theoretical and computational approach to investigate temporal behavior of a nonlinear polarization in perturbative regime induced by an intense and ultrashort pulsed electric field. First-principles time-dependent density functional theory is employed to describe the electron dynamics. Temporal evolution of third-order nonlinear polarization is extracted from a few calculations of electron dynamics induced by pulsed electric fields with the same time profile but different amplitudes. We discuss characteristic features of the nonlinear polarization evolution as well as an extraction of nonlinear susceptibilities and time delays by fitting the polarization. We also carry out a decomposition of temporal and spatial changes of the electron density in power series with respect to the field amplitude. It helps to get insight into the origin of the nonlinear polarization in atomic scale.
AMER INST PHYSICS, Mar. 2019, The Journal of Chemical Physics, 150 (9), 094101, English[Refereed]
Scientific journal
We develop a computational approach for ultrafast nano-optics based on first-principles time-dependent density functional theory. Solving Maxwell equations for light propagation and time-dependent Kohn-Sham equation for electron dynamics simultaneously, intense and ultrashort laser pulse interaction with a dielectric nano-structure is described taking full account of nonlinear effects. As an illustrative example, irradiation of a pulsed light on silicon nano-sphere system is presented.
E D P SCIENCES, 2019, XXI INTERNATIONAL CONFERENCE ON ULTRAFAST PHENOMENA 2018 (UP 2018), 205 (04023), EnglishInternational conference proceedings
- Lead, Dec. 2018, Proceedings of the 29th Symposium of Association for Condensed Matter Photophysics, 205 - 208, JapaneseOblique Light Incident in Maxwell+TDDFT Multiscale Simulation
Symposium
SALMON (Scalable Ab-initio Light-Matter simulator for Optics and Nanoscience, http://salmon-tddft.jp) is a software package for the simulation of electron dynamics and optical properties of molecules, nanostructures, and crystalline solids based on first-principles time-dependent density functional theory. The core part of the software is the real-time, real-space calculation of the electron dynamics induced in molecules and solids by an external electric field solving the time-dependent Kohn-Sham equation. Using a weak instantaneous perturbing field, linear response properties such as polarizabilities and photoabsorptions in isolated systems and dielectric functions in periodic systems are determined. Using an optical laser pulse, the ultrafast electronic response that may be highly nonlinear in the field strength is investigated in time domain. The propagation of the laser pulse in bulk solids and thin films can also be included in the simulation via coupling the electron dynamics in many microscopic unit cells using Maxwell's equations describing the time evolution of the electromagnetic fields. The code is efficiently parallelized so that it may describe the electron dynamics in large systems including up to a few thousand atoms. The present paper provides an overview of the capabilities of the software package showing several sample calculations.
ELSEVIER SCIENCE BV, 04 Apr. 2018, Computer Physics Communications, 235, 356 - 365, English[Refereed]
Scientific journal
- 情報処理学会, Mar. 2018, ハイパフォーマンス・コンピューティング研究会報告, Japanese電子動力学シミュレーションコードのメニーコアプロセッサ とGPUにおける性能比較
Symposium
- The Physical Society of Japan, 2018, Meeting Abstracts of the Physical Society of Japan, 73, 1483 - 1483, Japanese
Scientific journal
"ARTED" is an advanced scientific code for electron dynamics simulation which has been ported to various large-scale parallel systems including the "K" Computer, the ex-fastest supercomputer in the world, and many other MPP and cluster systems.In this paper, we describe ARTED's code optimization and performance evaluation applied to a large-scale cluster with Intel's latest many-core processor, KNL (Knights Landing), based on past research regarding porting ARTED to the KNC (Knights Corner) coprocessor. Code optimization for dominant computation has been thoroughly carried out in KNL to achieve the highest performance with detailed optimization such as memory access, vectorization for the AVX-512 instruction set, cache utilization, etc. For further tuning, we investigated various KNL-dedicated techniques such as combining MCDRAM/DDR4 memories and parallel vector summation.After detailed performance tuning on each core to achieve up to 25% of theoretical peak in the kernel part with 3-D stencil computation, we evaluated the application performance on the full system (25 PFLOPS of theoretical peak) of the KNL cluster "Oakforest-PACS" which is the largest KNL-based cluster in the world using the Intel Omni-Path Architecture. It shows excellent weak scaling with a dominant Hamiltonian performance of up to 4 PFLOPS (16% efficiency of the system) in double precision irrespective of simulation size as well as reasonable strong scaling on material simulations requiring high degree of parallelism.
SPRINGER INTERNATIONAL PUBLISHING AG, 2018, HIGH PERFORMANCE COMPUTING, ISC HIGH PERFORMANCE 2018, 10876, 205 - 225, English[Refereed]
International conference proceedings
- 情報処理学会, Jul. 2017, ハイパフォーマンス・コンピューティング研究会報告, Japanese電子動力学シミュレーションARTEDのKNLシステムOakforest-PACSでの全系性能評価
Symposium
We demonstrate a subwavelength position determination method for the terahertz region. Previously, we reported that an off-axis parabolic mirror generates a peculiar transient rotational distribution around the focus on the subwavelength scale. In the method proposed herein, the position is determined by measuring the electric field scattered by a sample placed at this rotational distribution. We perform a realistic numerical calculation and show that this method is feasible for a sample on the wavelength scale and can distinguish a displacement of the order of 0.01 wavelengths. This method can be easily implemented for micro and nanoscale measurement and processing in the terahertz region. (C) 2017 The Japan Society of Applied Physics
IOP PUBLISHING LTD, Jun. 2017, APPLIED PHYSICS EXPRESS, 10 (6), English[Refereed]
Scientific journal
This paper provides a detailed theoretical analysis of the unexpected transient divergent and rotational distributions of the focused electric field vector reported in Shibata et al (2015 Phys. Rev. A 92 053806). We reveal the physical origin of these distributions. More quantitatively, we derive the semi-analytic expressions and clarify how these distributions depend on the mirror size, offset angle, and the intensity distribution of the incident parallel light. We compare the formulas with numerical calculations and evaluate the area where linearity holds. If the wavelength and the mirror size are sufficiently shorter than the focal length, the radius of the linear area becomes longer than the wavelength. These formulas and evaluations are useful for studies, which require high spatio-temporal resolution.
IOP PUBLISHING LTD, Mar. 2017, JOURNAL OF OPTICS, 19 (3), English[Refereed]
Scientific journal
We propose that InGaN is superior to GaN as a host material for GaN-based red-light-emitting diodes (LEDs). In our previous paper, we proposed that codoping of Eu and a Mg and O pair generates an efficiently luminescent center in GaN. This is caused by the quantum confinement of the quantum dot constructions generated by the codoping method. The present report illustrates that InGaN allows the expansion of such electronic structures throughout the crystal owing to spontaneous phase decomposition. This can be used for self-organized fabrication and self-regenerated products. (C) 2017 The Japan Society of Applied Physics
IOP PUBLISHING LTD, Feb. 2017, JAPANESE JOURNAL OF APPLIED PHYSICS, 56 (2), English[Refereed]
Scientific journal
We present first-principles calculations for saturable absorption in graphite based on time-dependent density functional theory. Solving time-dependent Kohn-Sham equation for bulk graphite under a strong and ultrashort electric field, we have succeeded to investigate the temporal behavior of saturable absorption without any empirical parameters. It is found that the saturation takes place for ultrashort pulses of intensities stronger than 1010 W/cm2, in good agreement with observation. Mechanisms leading to the saturation is discussed from microscopic viewpoints.
OSA - The Optical Society, 2017, Optics InfoBase Conference Papers, 2017, English[Refereed]
International conference proceedings
We have investigated the spatial distribution of the polarization state of a terahertz electromagnetic wave focused by an off-axis parabolic mirror (OPM) in the focal plane. We employed polarization-resolved terahertz time-domain spectroscopy and found that a steep spatial variation in the polarization state appears slightly distant from the focus when a linearly polarized terahertz wave is focused. The spatial variation includes an abrupt change in the polarization state (states change between circular and linear polarizations) within a wavelength. The observed phenomena are confirmed by numerical calculations and are shown to be intrinsic to the reflection from the OPM. (C) 2016 The Japan Society of Applied Physics
IOP PUBLISHING LTD, May 2016, APPLIED PHYSICS EXPRESS, 9 (5), English[Refereed]
Scientific journal
A linearly polarized electromagnetic wave is found to form divergent and rotation fields after focused by an off-axis parabolic mirror. These distributions are generated within a subwavelength scale around the focus and at times when the electric field at the focus vanishes. We theoretically and experimentally show that not only the direction but also the structure of the distributions varies with the incident polarization. In addition, the distributions move in one direction with a phase velocity faster than the speed of light.
AMER PHYSICAL SOC, Nov. 2015, PHYSICAL REVIEW A, 92 (5), English[Refereed]
Scientific journal
A semiconductor bowtie nanoantenna acts as a high-quality cavity because a strongly enhanced field with a narrow spectral width appears at a nanogap region owing to exciton resonance. We theoretically investigate suitable antenna structures to obtain a strong field enhancement, and the following conditions are found: (i) the antenna structure is long in the direction of light polarization, and (ii) the tip structure near the nanogap is blunt. Condition (ii) is opposite to that for a metallic bowtie nanoantenna because the exciton wave function is distributed to avoid a narrow area near the sharp tip. These conditions are expected to be guidelines for designing efficient semiconductor nanoantennas for various applications. (C) 2015 Optical Society of America
OPTICAL SOC AMER, Apr. 2015, OPTICS LETTERS, 40 (8), 1695 - 1698, English[Refereed]
Scientific journal
We propose a nanogap structure composed of semiconductor nanoparticles forming an optical cavity. The resonant excitation of excitons in the nanoparticles can generate a localized strong light field in the gap region, also called "hot spot". The spectral width of the hot spot is significantly narrow because of the small exciton damping and the dephasing at low temperature, so the semiconductor nanogap structure acts as a high-Q cavity. In addition, the interaction between light and matter at the nanogap is significantly larger than that in a conventional microcavity, because the former has a small cavity-mode volume beyond the diffraction limit. We theoretically demonstrate the large and well-defined vacuum-Rabi splitting of a two-level emitter placed inside the semiconductor nanogap cavity: the Rabi splitting energy of 1.7 meV for the transition dipole moment of the emitter (25 Debye) is about 6.3 times larger than the spectral width. An optical cavity providing such a large and well-defined Rabi splitting is highly suited for studying characteristic features of the cavity quantum electrodynamics and for the development of new applications. (C) 2014 Optical Society of America
OPTICAL SOC AMER, Sep. 2014, OPTICS EXPRESS, 22 (19), 22470 - 22478, English[Refereed]
Scientific journal
We develop an electromagnetic (EM) simulation method based on a finite-element method (FEM) for an exciton confined to a semiconductor nanostructure. The EM field inside the semiconductor excites two transverse exciton polariton and a single longitudinal exciton at a given frequency. Established EM simulation methods cannot be applied directly to semiconductor nanostructures because of this multimode excitation; however, the present method overcomes this difficulty by introducing an additional boundary condition. To avoid spurious solutions and enhance the precision, we propose a hybrid edge-nodal element formulation in which edge and nodal elements are employed to represent the transverse and longitudinal polarizations, respectively. We apply the developed method to the EM-field scattering and distributions of exciton polarizations of spherical and hexagonal-disk quantum dots. (C) 2014 Optical Society of America
OPTICAL SOC AMER, Apr. 2014, OPTICS EXPRESS, 22 (8), 9450 - 9464, English[Refereed]
Scientific journal
- Lead, Dec. 2013, Proc. 24th Symp. Assoc. Condensed Matter Photophysics, 24, 459 - 462, JapaneseCalculation of Rabi Splitting by Semiconductor Nano-gap Cavity
Symposium
- Lead, Dec. 2012, Proc. 23th Symp. Assoc. Condensed Matter Photophysics, 23, 418 - 420, JapaneseSemiconductor nano-gap as a high-Q cavity
Symposium
- Lead, Dec. 2011, Proc. 22th Symp. Assoc. Condensed Matter Photophysics, 22, 285 - 289, JapaneseFinite Element Method for Electro Magnetic Field Scattering by Confined Exciton II
Symposium
- Lead, Dec. 2010, Proc. 21th Symp. Assoc. Condensed Matter Photophysics, 21, 391 - 394, JapaneseFinite Element Method for Electro Magnetic Field Scattering by Confined Exciton
Symposium
MISC
- Valley-dependent transport property of Stone--Wales and blister defects in graphene
Valleytronics, which makes use of the two valleys in graphenes, attracts much attention and the valley filter is expected to be central component in valleytronics. We investigate valley-dependent transport properties of the Stone-Wales (SW) and blister defects of graphenes by density functional theory calculations. It is found that the intervalley transition is perfectly suppressed in some structures although the intravalley scattering occurs by the defect states of the SW or blister defects. Using the tight-binding model, the perfect suppression of the intervalley transition in the SW and blister defects is explained by the sublattice symmetry between the A and B sites of the bipartite honeycomb lattice. In addition, introducing the additional carbon atoms to graphenes to form blister defects, the defect states appear near the Fermi level and the energies where the resonant scattering occurs on the $\mathrm{K}$ and $\mathrm{K}^\prime$ channel electrons split. Making use of this splits, the valley-dependent transport property will be achieved by local application of a gate voltage.
25 May 2023 - Density functional study of atomic and electronic structures of graphene on the FePd(001) surface
We report on the investigation of the atomic-scale structure and electronic properties of graphene(Gr) on the $L1_0$-FePd(001) interface using density functional theory. Although such hetero-interfaces have been experimentally synthesized, due to the significant lattice symmetry mismatch between the graphene and tetragonal alloy surface, a theoretical understanding of the optimal configuration of the carbon atoms is required. In this work, we consider various model structures of twisted and non-twisted FePd(001)/Gr interfaces. To evaluate the stability of our models, we analyzed the adsorption energies per carbon atom by performing structural optimizations, including van der Waals interactions. We found that the most stable structure had an adsorption energy of approximately $\approx -0.109~\mathrm{eV/atom}$ ($-10.5~\mathrm{kJ}/\mathrm{mol}$), and the energy barrier of the slide was smaller than $0.05~\mathrm{meV/atom}$. The FePd-graphene distance was approximately $2$ A., which successfully reproduced the experimental value.
20 Jan. 2022 - Attosecond-resolved petahertz carrier motion in semi-metallic TiS2
Knowledge about the real-time response of carriers to optical fields in solids is paramount to advance information processing towards optical frequencies or to understand the bottlenecks of light-matter interaction and energy harvesting. Of particular importance are semi-metals and transition metal dichalcogenides due to their small band gap and high carrier mobility. Here, we examine the opto-electronic response of TiS2 to optical excitation by means of attosecond soft x-ray spectroscopy at the L-edges of Ti at 460 eV. Using weak-field infrared single-photon excitation, we examine conditions that avoid excessive excitation, but still attain efficient injection of 0.2% of valence band carriers into the lowest lying conduction band. We demonstrate that the efficient injection and the high- carrier mobility of the conduction band permits leveraging the material to achieve petahertz-speed opto-electronic control of its carriers. Our results are an important step towards understanding the dynamics of carriers and their control under field conditions that are realistic for device implementation in semi-metallic layered materials, thus they may lead to ultrafast and optically controlled field-effect devices and sensors.
20 Aug. 2018Technical report
- The Physical Society of Japan, 2017, Meeting Abstracts of the Physical Society of Japan, 72 (0), 1149 - 1149, JapaneseOne-dimensional subwavelength positioning using off-axis parabolic mirror
- The Physical Society of Japan, 2017, Meeting Abstracts of the Physical Society of Japan, 72 (0), 1127 - 1127, Japanese
<p>第一原理間電子状態計算法により強電場下の電子ダイナミクスの理論予測が可能になってきている。我々は、これをFDTDベースの電磁界計算手法と組み合わせたマルチスケールシミュレーション法を独自に提案した。本発表では同手法をもちいた半導体薄膜における光透過・吸収過程の解析について紹介する。</p>
The Physical Society of Japan, 2017, Meeting Abstracts of the Physical Society of Japan, 72 (0), 1438 - 1438, Japanese<p>第一原理間電子状態計算法により強電場下の電子ダイナミクスの理論予測が可能になってきている。我々はフェムト秒パルス印加のもとで時間依存密度汎関数理論に基づく実時間第一原理計算を行い、各種パルス形状・強度における誘電分極の時間および空間分布を探査し、それをもとに非線形光学定数の予測、およびその発生メカニズムについて論ずる。</p>
The Physical Society of Japan, 2016, Meeting Abstracts of the Physical Society of Japan, 71 (0), 1432 - 1432, Japanese<p>放物面鏡で直線偏光、一様強度の平面波を集光すると、ある時刻において焦点近傍に発散・回転型の電場ベクトル分布が生成されることを報告した。ガウス分布の場合に、その中心座標によって集光電場ベクトルがどうなるかを調べた。焦点近傍での強度分布はほとんど変わらないが、発散・回転の構造は大きく変化することが分かった。その結果を定量的、定性的に説明する。</p>
The Physical Society of Japan, 2016, Meeting Abstracts of the Physical Society of Japan, 71 (0), 1341 - 1341, Japanese- The Physical Society of Japan, 2016, Meeting Abstracts of the Physical Society of Japan, 71 (0), 1542 - 1542, Japanese
- The Physical Society of Japan, 2016, Meeting Abstracts of the Physical Society of Japan, 71 (0), 1543 - 1543, Japanese
- The Physical Society of Japan, 2016, Meeting Abstracts of the Physical Society of Japan, 71 (0), 1544 - 1544, Japanese
- The Physical Society of Japan, 2015, Meeting Abstracts of the Physical Society of Japan, 70 (0), 1038 - 1038, Japanese
- The Physical Society of Japan, 2015, Meeting Abstracts of the Physical Society of Japan, 70 (0), 1189 - 1189, Japanese
- The Physical Society of Japan, 2015, Meeting Abstracts of the Physical Society of Japan, 70 (0), 1190 - 1190, Japanese
- The Physical Society of Japan, 2013, Meeting Abstracts of the Physical Society of Japan, 68 (0), 228 - 228, Japanese
- The Physical Society of Japan, 2013, Meeting Abstracts of the Physical Society of Japan, 68 (0), 811 - 811, Japanese
- The Physical Society of Japan, 2013, Meeting Abstracts of the Physical Society of Japan, 68 (0), 697 - 697, Japanese
- The Physical Society of Japan, 2012, Meeting Abstracts of the Physical Society of Japan, 67 (0), 675 - 675, Japanese
- The Physical Society of Japan, 2011, Meeting Abstracts of the Physical Society of Japan, 66 (0), 783 - 783, Japanese
- The Physical Society of Japan, 2010, Meeting Abstracts of the Physical Society of Japan, 65 (0), 696 - 696, Japanese
Books etc
- Contributor, p103-133, Springer, 22 Jul. 2021, ISBN: 3030715159Progress in Nanophotonics 6 (Nano-Optics and Nanophotonics)
Presentations
- The 70th JSAP Sprint Meeting 2023, 17 Mar. 2023, Japanese非線形ナノフォトニクスのための第一原理シミュレーション
Oral presentation
- 第70回応用物理学会春季学術講演会, 16 Mar. 2023, Japaneseステップを持つSiC MOS界面におけるNO窒化処理の移動度改善効果の解析
Oral presentation
- 第１６回強的秩序とその操作に関わる研究, 28 Jan. 2023, JapaneseFirst-principles transport calculation of magneto-resistance ratio in FePd(001)/Graphene magnetic tunnel junction
Poster presentation
- The 33th Symposium of Association for Condensed Matter Photophysics, 10 Dec. 2022, JapaneseFirst-principles simulation of nonlinear optical properties of III-V semiconductors
Poster presentation
- The 30th Anniversary Symposium of the Center for Computational Sciences at the University of Tsukuba, 14 Oct. 2022, EnglishAb-initio study of nanoscale optical and electronics devices
Poster presentation
- The 30th Anniversary Symposium of the Center for Computational Sciences at the University of Tsukuba, 14 Oct. 2022, EnglishDevelopment of first-principles calculation code RSPACE and simulation for transport property of interfaces
Poster presentation
- 強的秩序とその操作に関わる第15回夏の学校, 23 Sep. 2022, JapaneseFePd/グラフェンの異種結晶界面状態の第一原理計算
Poster presentation
- The 83rd JSAP Autumn Meeting 2022, 23 Sep. 2022, JapaneseFirst-principles study on the electronic and magnetic properties of FePd/Graphene heterogeneous interface
Oral presentation
- The 83rd JSAP Autumn Meeting 2022, 21 Sep. 2022, JapaneseFirst-principles study on NO-annealed SiC/SiO2 interface atomic structure
Oral presentation
- The 83rd JSAP Autumn Meeting 2022, 21 Sep. 2022, JapaneseFirst-principles simulation of nonlinear optical properties of solid crystals
Oral presentation
- The Physical Society of Japan 2022 Annual (77th) Meeting, 16 Mar. 2022, JapaneseFirst principle electron dynamics simulation for the light propagation in the nanoscale semiconducting material
Oral presentation
- 強的秩序とその操作に関わる研究グループ第13回研究会, 04 Jan. 2022, JapaneseFePd(001)/Graphene の第一原理計算による磁気特性の計算
Poster presentation
- The 32th Symposium of Association for Condensed Matter Photophysics, 10 Dec. 2021, JapaneseFirst-principles study of ultrafast saturable absorption of 2D transition metal dichalcogenide monolayers
Poster presentation
- International Workshop on DIELECTRIC THIN FILMS FOR FUTURE ELECTRON DEVICES (IWDTF), 16 Nov. 2021, EnglishDFT Study on Defect Structures at SiC(000-1)/SiO2 Interface after Wet Oxidation
Oral presentation
- JPS2021 Autumn Meeting, 23 Sep. 2021, JapaneseFirst-principles study of ultrafast saturable absorption of transition metal dichalcogenide monolayers
Oral presentation
- The 82nd JSAP Autumn Meeting 2021, 22 Sep. 2021, EnglishAnisotropic orbital moment induced at graphene / L10-alloy hybrid interface
Poster presentation
- JPS2021 Autumn Meeting, 22 Sep. 2021, JapaneseElectronic structure calculation of FePd(001)/Graphene based on first-principles study
Oral presentation
- JPS2021 Autumn Meeting, 22 Sep. 2021, JapaneseFirst-principles study on conduction property of graphene blister
Oral presentation
- The 82nd JSAP Autumn Meeting 2021, 11 Sep. 2021, JapaneseFirst-principles study on electronic structure of SiC/𝐒𝐢𝐎𝟐 step interface
Oral presentation
- The 82nd JSAP Autumn Meeting 2021, 10 Sep. 2021, JapaneseDirect writing of high-dense NV centers in diamond by femtosecond laser irradiation
Oral presentation
- 2021 International Conference on Solid State Devices and Materials (SSDM2021), 08 Sep. 2021, EnglishDFT study on structure and anisotropy of high N-atom density layer in 4H-SiC
Oral presentation
- 新合同ワーキング, 21 Mar. 2021, JapaneseGraphene/FePd(001)表面の構造探索について
- 応用物理学会第68回春季学術講演会, 18 Mar. 2021, Japanese第一原理計算によるwet酸化SiC(000-1)/SiO2界面の欠陥構造解析
Oral presentation
- The Physical Society of Japan 2021 Annual (76th) meeting, 12 Mar. 2021, JapaneseFirst-principles study on Graphene/FePd(001) interface structure
Oral presentation
- 強的秩序とその操作に関する第12回講演会, 04 Jan. 2021, JapaneseFirst-principles study on Graphene/FePd(001) interface structure
Poster presentation
- The Physical Society of Japan (JPS) 2020 Autumn Meeting, 11 Sep. 2020, JapaneseFirst-principles study of the nitrogen defects in 4H-SiC MOS
Oral presentation
- SPIE Photonics Europe, 2020, 30 Mar. 2020, EnglishTransient attosecond soft-X-ray spectroscopy in layered semi-metals
Oral presentation
- 第67回応用物理学会春季学術講演会, 15 Mar. 2020, JapaneseFirst-Principles Study of Nitrogen Annealed SiC MOS structure
Oral presentation
- 鳩山サイエンスフォーラム, 08 Jan. 2020, Japanese, 東京電機大学, 東京電機大学, Domestic conference光科学の数値実験室をつくる
[Invited]
Invited oral presentation
- iSPN2019, 12 Nov. 2019, English, International conferenceDevelopment of Multiscale First-Principles Approach for Optical Response in Nanostructure
Oral presentation
- 27th International Conference on Advanced Laser Technologies, 16 Sep. 2019, English, International conferenceMaxwell+TDDFT multiscale method for light-propagation in solids
[Invited]
Invited oral presentation
- The Physical Society of Japan (JPS) 2019 Autumn Meeting, 12 Sep. 2019, Japanese, Domestic conferenceFirst-principles calculation of the light matter interaction between thin-film graphite and intense laser pulse
Oral presentation
- ポスト「京」重点課題7第5回シンポジウム, 09 Aug. 2019, Japanese, Domestic conference大規模計算をもちいた極限パルス光・固体物質相互作用の第一原理シミュレーション
Poster presentation
- MI^2I・元素戦略・ポスト京・計算物質科学コンソ・合同Working, 20 Jul. 2019, Japanese, Domestic conference固体物質の光学応答第一原理計算 〜RNNによる誘電応答学習の提案〜
Others
- 光量子科学連携研究機構 (UTripl) セミナー, 01 Jul. 2019, Japanese, Domestic conferenceTDDFT による第一原理電子ダイナミクス計算とナノフォトニクスへの適用に向けて
Public discourse
- The physical society of Japan, 2019 Annual (74th) Meeting, 15 Mar. 2019, Japanese, University of Kyushu, Domestic conferenceMaxwell+TDDFT Multiscale Simulation for Nanophotonics
Oral presentation
- APS March Meeting 2019, 05 Mar. 2019, English, International conferenceMaxwell+TDDFT multiscale simulation for optical response of nanomaterials
Oral presentation
- The 1st R-CCS International Symposium, 18 Feb. 2019, English, International conferencearge-scale ab-initio simulation for nano-optics based on time-dependent density functional theory
Poster presentation
- MI2Iマテリアルズ探索グループ拡大合同Working「ナノテクノロジーにおけるマテリアルズ・インフォマティクス・ネットワーク」, 17 Feb. 2019, Japanese, Domestic conference第一原理電子ダイナミクス計算に基づくナノフォトニクスシミュレーション
Oral presentation
- International Workshop on Massively Parallel Programming for Quantum Chemistry and Physics 2019, 16 Jan. 2019, English, International conferenceAb-initio large-scale computational approach for ultrafast dynamics in Nano-Optics
[Invited]
Invited oral presentation
- 「次世代の産業を支える新機能デバイス・ 高性能材料の創成(CDMSI）」第4回シンポジウム, 17 Dec. 2018, Japanese, 東大物性研, Domestic conferenceTDDFT による非線形光学応答の時空間空間解析
Poster presentation
- The 29th Symposium of Association for Condensed Matter Photophysics, 08 Dec. 2018, Japanese, 京都大学宇治おうばくプラザ, Domestic conferenceOblique Light Incident in Maxwell+TDDFT Multiscale Simulation
Poster presentation
- AIEDS18, 16 Nov. 2018, English, Tsukuba, International conferenceMaxwell+TDDFT Ab initio Multiscale Simulation and Application to Nano-optics
[Invited]
Invited oral presentation
- AIEDS18, 14 Nov. 2018, English, International conferenceSpatio-Temporal Analysis of Nonlinear Optical Responses by Time-Dependent Density Functional Theory
Poster presentation
- The Physical Society of Japan 2018 Autumn Meeting, 10 Sep. 2018, Japanese, 同志社大学, Domestic conferenceFirst principle electron dynamics simulation for the oblique light propagation in the semiconducting material
Oral presentation
- 第３回CDMSI（ポスト「京」重点課題（７））シンポジウム, 19 Jul. 2018, Japanese, University of Tokyo, Domestic conference第一原理電子ダイナミクス計算による ナノフォトニクスシミュレーション
Oral presentation
- EXCON2018, 09 Jul. 2018, English, International conferenceAb-initio large-scale computational approach for ultrafast dynamics in nano-structures
Oral presentation
- 日本物理学会春季大会, 22 Mar. 2018, Japanese, 東京理科大, Domestic conferenceMaxwell+TDDFTマルチスケール第一原理計算 (III)〜３次元ナノ構造と斜方向光入射〜
Oral presentation
- 第2回CDMSI(ポスト「京」重点課題（7）)研究会, 05 Dec. 2017, Japanese, University of Tokyo, Domestic conferenceナノ構造体に対する高強度パルス光励起ダイナミクスの大規模計算
Poster presentation
- 日本物理学会秋期大会, 21 Sep. 2017, Japanese, Iwate University, Domestic conference半導体３次元ナノ構造の高強度光パルス伝搬に関する第一原理マルチスケール計算
Oral presentation
- 第3回CDMSI（ポスト「京」重点課題（７））シンポジウム, 11 Jul. 2017, Japanese, Domestic conference半導体３次元ナノ構造の高強度光パルス伝搬に関する第一原理マルチスケール計算
Oral presentation
- Interdisciplinary symposium on modern density functional theory (IDFT), 19 Jun. 2017, English, International conferenceMaxwell+TDDFT multiscale method for light-matter interaction: light propagation in the microscopic semiconducting crystal
Oral presentation
- CLEO2017, 14 May 2017, English, San Jose, USA,, International conferenceFirst-principles calculations for saturable absorption in graphite
Poster presentation
- 日本物理学会, 2017, Japanese, Domestic conferenceMaxwell+TDDFTマルチスケール第一原理計算による二次元光伝播シミュレーションの試み
Oral presentation
- 日本物理学会, 2017, Japanese, Domestic conference放物面鏡による集光を利用した一次元方向のサブ波長の位置決め方法について
Oral presentation
- 日本物理学会, 2016軸外し放物面鏡集光時の回転・発散電場の出現と時間変化
- 日本物理学会, 2016, Japanese, Domestic conference放物面鏡による集光電場ベクトル分布の物理的起源とその表式の一般化について
Oral presentation
- 日本物理学会, 2016, Japanese, Domestic conference軸外し放物面鏡集光時のテラヘルツ電場ベクトル時空間分布の周波数依存性
Oral presentation
- 日本物理学会, 2016, Japanese, Domestic conference放物面鏡による集光における、入射光の強度分布と集光電場ベクトル分布の関係について
Oral presentation
- 日本物理学会, 2016, Japanese, Domestic conference第一原理電子ダイナミクス計算による非線形光学定数の予測
Oral presentation
- 日本物理学会, 2015, Japanese, Domestic conferenceユーロピウム酸素共添加窒化ガリウムの磁気状態
Oral presentation
- Physical Society of Japan, 28 Sep. 2013, JapaneseVacuum field Rabi splitting with semiconducting nano-gap cavity
Oral presentation
- Physical Society of Japan, 27 Mar. 2013, JapaneseThe near field enhancement of semiconductor nano-gap
Oral presentation
- Physical Society of Japan, Sep. 2012, JapaneseFinite Element Method for Excitonic Mediums III
Oral presentation
- 日本物理学会, Sep. 2011, JapaneseThe Finite Element Method for Excitonic Materials II
Oral presentation
- Physical Society of Japan, Sep. 2010, JapaneseThe electromagnetic field analysis of excitonic material
Oral presentation
Association Memberships
Works
- 27 Jan. 2020 - Present
A program to visualize input files of RSPACE, a first-principles density functional theory (DFT) program for solid and molecule systems.
An open-source computer program for ab-initio quantum-mechanical calculations of electron dynamics at the nanoscale
Research Projects
- Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Grant-in-Aid for Scientific Research (B), University of Tsukuba, Apr. 2020 - Mar. 2024, Coinvestigator第一原理計算が拓く多元的な極限ナノフォトニクス
- University of Tsukuba, Multidisciplinary Cooperative Research Program (MCRP) 2022, Center of Computational Sciences, Apr. 2022 - Mar. 2023, Principal investigatorFirst-principles design of nanoscale optical and spintronics devices
- Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Early-Career Scientists, Grant-in-Aid for Early-Career Scientists, Kobe University, Apr. 2020 - Mar. 2023, Principal investigator半導体メタ表面における光物質相互作用の第一原理予測
- CCS, University of Tsukuba, Multidisciplinary Cooperative Research Program 2021, Apr. 2021 - Mar. 2022, Principal investigatorAb-initio study of nanoscale optical and electronics devices
- Iketani Science and the Technology Foundation, 単年度助成, 神戸大学, Apr. 2020 - Mar. 2021, Principal investigator第一原理計算による炭素材料ナノ構造の光学応答評価
- Center for Computational Sciences (CCS), University of Tsukuba, Multidisciplinary Cooperative Research Program 2020, Apr. 2020 - Mar. 2021, Principal investigatorDesign of Nanophotonic Device by Large-Scale Ab-initio Calculation
- CCS, University of Tsukuba, Multidisciplinary Cooperative Research Program, Apr. 2019 - Mar. 2020, Principal investigator第一原理電子ダイナミクス計算によるメタ表面と極限パルス光の相互作用
Competitive research funding
- Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Grant-in-Aid for Scientific Research (B), Apr. 2016 - Mar. 2020, Coinvestigator大規模第一原理スピン輸送シミュレーターの開発と革新的デバイス用界面構造の設計
界面電子状態の理解の深化と次世代デバイスとして期待されているスピントロニクスデバイスの高機能化・産業化に貢献すべく、電子論からデバイス用界面の機能予測ができる大規模高精度第一原理計算手法の開発とこれを用いた界面機能予測シミュレーションを実施している。平成30年度は、これまで開発・改良を続けてきたRSPACEを用いて、次に挙げる2種類のナノ構造の輸送特性を調べた。 1つ目は、実験グループと協力して、trimethylenedipyridineと、この分子が重合したpolyvinylpyridineの分子架橋系の電気伝導特性を調べた。電極/分子界面における原子構造を、実験的に予想される架橋構造をもとに第一原理計算により決定し、重合による架橋系の電子状態と伝導特性への影響を調べた。そして、重合による電気伝導度への影響がわずかであるという実験結果に符合する結果を得た。 2つ目は、二次元材料を用いた磁気トンネル接合の輸送特性を調べた。グラフェンをはじめとする二次元系材料は、スピントロニクスデバイスのチャネル材料として期待されている。本課題では、グラフェン及びh-BNをNi及びCoの強磁性金属で挟んだ磁気トンネル接合の磁気抵抗比を調べた。そして、Ni電極/グラフェン/Ni電極の系で磁気抵抗比が50%、Ni電極/h-BN/Ni電極の系で43%という高い値が得られることを明らかにし、グラフェンのような二次元系材料を用いた磁気トンネル接合構造がスピンフィルターとして有望であることを示した。
Social Contribution
- Lecturer, 20 Feb. 2023 - 24 Feb. 2023The 42-nd Computational Materials Design (CMD) Workshop
- Lecturer, 05 Sep. 2022 - 08 Sep. 2022The 41-st Computational Materials Design (CMD) Workshop
- Lecturer, 21 Feb. 2022 - 25 Feb. 2022The 40-th Computational Materials Design (CMD) Workshop
- Lecturer, 06 Sep. 2021 - 10 Sep. 2021The 39-th Computational Materials Design (CMD) Workshop
- Lecturer, 22 Feb. 2021 - 26 Feb. 2021The 38-th Computational Materials Design (CMD) Workshop
- Lecturer, 17 Mar. 2020 - 22 Mar. 202036th Computational Material Design (CMD) Workshop
- Lecturer, 02 Sep. 2019 - 05 Sep. 201935th Computational Materials Design(CMD®) Workshop
- Lecturer, 18 Feb. 2019 - 22 Feb. 201934th Computational Materials Design(CMD®) Workshop
- Lecturer, 03 Sep. 2018 - 07 Sep. 2018The 33-th Computational Materials Design (CMD) Workshop
- Organizing member, 23 Sep. 2017 - 27 Sep. 2017Junjirou Kanamori Memorial International Symposium (Local Organizing Committee)
Media Coverage
- 日本経済新聞番組, 日本経済新聞 電子版, 06 Sep. 2022, 速報, 電子の電気と磁気の性質を利用するスピントロニクス素子は、現在の電子素子に比べて桁違いに少ない消費電力と、桁違いに高い演算速度を実現すると期待されています。その素子には、強磁性合金とグラフェンなどの二次元物質を接合する構造が提案されています。しかし強磁性合金とグラフェンの界面構造が未解明のため、最適な特性の素子を設計することはできませんでした。 神戸大学大学院工学研究科の植本光治助教、小野倫也教授、大学院生の安達隼人氏らと東北大学の永沼博准教授らの研究グループは、密度汎関数理論に基づく第一原理計算により、鉄パラジウム合金とグラフェンの異種結晶界面(FePd/Gr)の構造および特性のシミュレーションを行いました。 FePd/Grは最近実験的に合成された新材料で、スピントロニクスデバイスへの応用が期待されています。本研究では、これまでの実験では明らかにされていなかったFePd.Gr界面の炭素原子配置として考えられるいくつかのモデルを、計算により予測しました。 その結果、予測したFePd/Gr吸着距離の理論値は、実験値(約2Å＝100億分の2)をよく再現していること、また、先行実験で報告されている「異なる結晶界面の"つよく"・"しなやか"な結合」の存在を確認することができました。今後、本研究で提案された計算モデルは、強磁性トンネル接合素子などの機能予測や最適化、材料探索に役立つことが期待されます。この研究成果は、9月1日に Journal of Applied Physics でオンライン掲載されました。
Internet
- 東北大学・神戸大学ほか（プレスリリース）, 02 Mar. 2022
Paper
- Other than myself, 筑波大学・神戸大学（プレスリリース）, Jan. 2022
Internet
- Myself, 神戸大学（プレスリリース）, Dec. 2021, 神戸大学大学院工学研究科の小野倫也教授、植本光治助教、大学院生の小松直貴さんらと、北海道大学の江上喜幸助教らの研究グループは、第一原理計算に基づいたSiC中の高密度窒素層の構造モデルの提案を行いました。この成果は、SiC半導体デバイスの製造時の窒素アニールの働きについて理解を深めることにつながります。この研究成果は、11月30日に Journal of the Physical Society of Japan に掲載されました。
Internet
- Other than myself, 筑波大学（プレスリリース）, Mar. 2019, 筑波大学計算科学研究センター 矢花一浩教授の研究グループと、大学共同利用機関法人自然科学研究機構分子科学研究所 故 信定克幸准教授の研究グループは、国立研究開発法人量子科学技術研究開発機構関西光科学研究所、東京大学工学系研究科、マックスプランク物質構造動力学研究所、ウィーン工科大学、ワシントン大学の研究者らと共同て、物質科学の第一原理計算法に基づき、先端の光科学研究に役立つソフトウェアSALMONを開発しました。
Internet