Announcement2023.05.31
Prof. Dr. Mathias Kläui (Johannes Gutenberg University Mainz, Germany) will give a seminar talk[Abstract].
Date：2023.05.31(Wed.) 15:15
Place：Bldg. 55N(North Tower), 1st floor, 2nd Conference Room, Nishi-Waseda campus, Waseda university
Title：Skyrmions in Spin-Orbitronics and Orbitronics – novel science and applications in memory & non-conventional computing
Speaker：Prof. Dr. Mathias Kläui（Johannes Gutenberg-Universität Mainz, Germany）

Announcement2023.05.23 The following book (in Japanese) was published from NTS publishers, Japan. Prof. Mochizuki provided a section contribution about the skyrmions [web],[pamphlet]。 Book title: Spintronics Handbook ―Fundamentals and Applications―(760 pages) ISBN 978-4-86043-842-5, e-Book ISBN 978-4-86043-843-2

2023.05.06
Prof. Mochizuki gave an invited talk at the 8th International Conference on Superconductivity and Magnetism (ICSM2023) held in May 4-11 at Liberty Hotels Lykia in Ölüdeniz, Turkey.

Title：Dynamical Switching, Creation and Manipulation of Topo Magnetism in Spin-Charge Coupled Magnets

2023.04.17 The following paper was published in Physical Review B. In this paper, we propose versatile and powerful machine learning methods for detecting the Berezinskii-Kosterlitz-Thouless transition and the second-order transition in the XXZ model and demonstrate their efficiencies. The XXZ model has three-dimensional spin vectors, which makes it much more difficult to detect phase transitions than the XY and clock models with two-dimensional spin vectors. The proposed methods, called ``temperature identification method" and ``phase classification method", can detect phase transitions in the XXZ model with minimal prior knowledge of the model and prior processing of the data. Y. Miyajima and M. Mochizuki Physical Review B 107, 134420/1-16 (2023). Title：Machine-learning detection of the Berezinskii-Kosterlitz-Thouless transition and the second-order phase transition in XXZ models

2023.04.01
Ryui KANEKO (Research Associate Professor) and Yuya OMINATO（Lecturer at WIAS）joined our group. Tatsuya IGUCHI and Ryo HAMANO also joined as batchelor students. Mu-Kun LI has been promoted to a lecturer.[Member]

2023.03.31
Jean-Baptiste MORÉE (Research Lecturer) and Michael Thobias SCHMID (Research Lecturer) have moved our from our group.

2023.03.26
Two students, Yuto Uwabo and Rintaro Eto, have completed their master's degree in the Department of Physics and Applied Physics at Waseda University[Album].

2023.03.26
Two students, Masaki Tanabe and Hirotaka Yano, graduated from the Department of Physics and the Department of Applied Physics, respectively, at Waseda University[Album].

2023.03.26
Rintaro Eto (M2) was selected as a winner of the Koizumi Prize for master's thesis in the Department of Physics and Applied Physics.
[Photo1], [Photo2]

2023.03.26
Rintaro Eto (M2) received the 64th Azusa Ono Memorial Prize for Academic Achievement[Album].

The Azusa Ono Memorial Prize is a student prize established by Waseda University, and is the most prestigious prize among the prizes awarded to students. It was established in 1958 to commemorate the achievements of Azusa Ono, who was a political scientist and worked with Shigenobu Okuma to establish the Tokyo Senmon Gakko, the predecessor of Waseda University.

【Achievement eligible for the award】
R. Eto, R. Pohle, and M. Mochizuki, Phys. Rev. Lett. 129, 017201/1-7 (2022).
Low-Energy Excitations of Skyrmion Crystals in a Centrosymmetric Kondo-Lattice Magnet: Decoupled Spin-Charge Excitations and Nonreciprocity

2023.03.22-25
The following oral presentations were given by our group members in The Physical Society of Japan (JPS) 2023 Spring meeting (Online)
Numb.: 22aC1-3
Title: Machine-Learning Detection of the phase transitions:The second-order transition and the Berezinskii-Kosterlitz-Thouless transition in the two-dimensional classical XXZ models (in Japanese)
Speakers: Yusuke Miyajima, Masahito Mochizuki

Numb.: 23aC2-10
Title: Reservoir Computing with Spin Waves in a Skyrmion Crystal (in English)
Speakers: Mu-Kun Lee, Masahito Mochizuki

Numb.: 23aC2-11
Title: Thiele analysis of the current-induced skyrmion creation and dynamics with the spin-orbit torques (in Japanese)
Speakers: Yuto Uwabo, Masahito Mochizuki

Numb.: 23pE2-5
Title: Theoretical study on photoinduced topological phases in a ferrimagnetism-induced Dirac half-metallic state: Analysis of the periodic Anderson model (in Japanese)
Speakers: Rintaro Eto, Masahito Mochizuki

Numb.: 24pE1-3
Title: Theoretical studies on the photoinduced half-valley metallic phase in α-type organic salt (in Japanese)
Speakers: Keisuke Kitayama, Masao Ogata, Yasuhiro Tanaka, Masahito Mochizuki

2023.03.17
A farewell party was held at Rihga Royal Hotel, Kanshi-so[Album].


2023.03.15-18
The following oral presentation were given by our group members in The 70th JSAP (The Japanese Society of Applied Physics) Spring Meeting 2023 (Yotsuya Campus, Sophia University + Online)
Numb.: 16a-D419-9
Title: Theoretical study on controlled creations and dynamics of magnetic skyrmions with the spin-orbit torques (in Japanese)
Speakers: Yuto Uwabo, Masahito Mochizuki

2023.03.13 The following paper was published in a Letter section of Physical Review B. In this paper, we theoretically predicted and demonstrated that by irradiating a skyrmion crystal confined in a circular disk with light or electron beams, we can generate a DC electromotive force in the radial direction from a steady rotational motion in the presence of temperature gradient introduced by the irradiation. This is the world's first proposal of the thermoelectric function of magnetic skyrmions. J. Matsuki and M. Mochizuki Physical Review B 107, L100408 (2023). Title：Thermoelectric effect of a skyrmion crystal confined in a magnetic disk

2023.03.05-10
The following oral presentations were given by our group members in APS March Meeting 2023 (Las Vegas, Nevada, USA).
Numb.: M44.00005 (9:36 AM–9:48 AM, March 8 (Wed), 2023, Room 316)
Title: Dynamical switching of magentic topology in microwave-driven itinerant magnet
Speakers: Rintaro Eto, Masahito Mochizuki

Numb.: W54.00006 (4:24 PM–4:36 PM, March 9 (Thu), 2023, Room 306)
Title: Reservoir Computing with Spin Waves in a Skyrmion Crystal
Speakers: Mu-Kun Li, Masahito Mochizuki

2023.02.19 The following paper was published in npj Quantum Materials. In this paper, we studied the electromagnon excitations in a multiferroic material CuO in collaboration with an experimental group in France. This material exhibits a multiferroic phase near the room temperature. We constructed its microscopic spin model that can quantitatively reproduce the observed multi-step magnetoelectric phase transitions. Using this model, we succeeded in fully reproducing the experimental far-infrared spectra of electromagnon excitations in the multiferroic phase at finite temperatures. M. Verseils, P. Hemme, D. Bounoua, R. Cervasio, J-B. Brubach, S. Houver, Y. Gallais, A. Sacuto, D. Colson, T. Iijima, M. Mochizuki, P. Roy and M. Cazayous npj Quantum Materials　8, 11 (2023). Title：Stabilizing electromagnons in CuO under pressure

2023.02.03
The graduation thesis presentations of the Department of Applied Physics and the Department of Physics were held. Two students from our group, Masaki Tanabe and Hirotaka Yano, gave presentations.

【Bachelor Thesis Titles】
Masaki Tanabe ``Theory of helimagnetism engineering in chiral magnets"
Hirotaka Yano ``Theoretical study on the magnetic phases in a skyrmionic material with a polar tetragonal crystal structure"

2023.02.04
The master's thesis presentations of the Department of Physics and Applied Physics were held. Two students from our group, Yuto Uwabo and Rintaro Eto, gave presentations.

【Mater's Thesis Titles】
Yuto Uwabo ``Theoretical study on the creation and motion of skyrmions driven by the spin-orbit torque"
Rintaro Eto ``Theory of low-energy excitations and photocontrol of topological spin textures in spin-charge coupled magnets"

2023.01.27
Prof. Mochizuki gave an invited talk at the workshop held on January 27 at Tokyo Satellite Campus of Nagaoka University of Technology.

Title：Reservoir-type information processing device utilizing spin-wave propagation in a skyrmion crystal (in Japanese)

2023.01.17
Yusuke Miyajima (PhD student) gave an oral presentation at 2023 Annual Meeting of the Physical Society of Taiwan (TPS2023) held in Taiwan (Jan. 16-18, 2023).

Title: Proposal of a machine learning method for detection of the Berezinskii-Kosterlitz-Thouless transitions in the q-state clock models

2023.01.11
Xichao ZHANG has joined our lab. as a postdoc/research lecturer [Members]. He will work on the JST, CREST research project Creation of a new topological magnetic science for Beyond Skyrmion".

2022.12.24
Prof. Mochizuki gave an invited talk at a workshop about new trends in the chiral materials science held in ISSP, the University of Tokyo (Dec.22-24, 2022).

Title: Chiralities and dynamics in the multiferroics (in Japanese)

2022.12.22
Keisuke Kitayama (Former student member) gave an oral presentation at a winter school for young researchers on organic materials [web] held at Okazaki Conference Center in National Institutes of Natural Sciences (NINS), Okazaki, Aichi, Japan (December 22-23, 2022).

Title: Theoretical studies of photoinduced topological phase transitions in organic salt α-(BEDT-TTF)₂I₃ (in Japanese)

2022.12.19
BO Lan has joined our lab. as a research student [Members]. He is a third-year Ph.D student in the Northeastern university in China. He will stay in our lab for a year as a postgraduate student funded by China Scholarship Council.

2022.12.07
Li Mu-Kun (Postdoc・Research Lecturer) gave an oral presentation at an international workshop ``The Workshop on Innovative Nanoscale Devices and Systems (WINDS2022)" held on the Island of Kaua'i, Hawaii (December 4-9, 2022).

Title: Microwave-Driven Phenomena of Magnetic Skyrmions

2022.11.15
Keisuke Kitayama (Former student member) gave a poster presentation at the YIPQS long-term and Nishinomiya-Yukawa memorial workshop ``Novel Quantum States in Condensed Matter 2022" (NQS2022) held at Yukawa Institute for Theoretical Physics (YITP), Kyoto university, Kyoto, Japan (Oct. 31-Dec. 2, 2022).

Title: Theoretical studies of photoinduced topological phase transitions in organic salt α-(BEDT-TTF)₂I₃

2022.11.02
Prof. Mochizuki gave an oral presentation at an international workshop ``The 67th Annual Conference on Magnetism and Magnetic Materials (MMM2022)" held in Hyatt Regency Minneapolis, MN, USA (Oct.31-Nov.4, 2022).

Title: Microwave-Driven Phenomena of Magnetic Skyrmions

2022.09.29
Keisuke Kitayama (Former student member) gave an oral presentation at an international workshop The 14th International Symposium on Crystalline Organic Metals, Superconductors and Magnets (ISCOM2022)" held in Le Pouliguen, France (September 25-30, 2022).

Title: Theoretical studies of photoinduced topological phase transitions in organic salt α-(BEDT-TTF)₂I₃

2021.09.28
Rintaro Eto (second-year master's student) has been selected as a JSPS Research Fellow DC1 for the coming year.

2021.09.26 The following paper has been published in Journal of the Physical Society of Japan. In this paper, we theoretically predicted possible occurrence of a new-type photoinduced topological phase transition in the organic salt α-(BEDT-TTF)2I3 irradiated by elliptically polarized laser light. We found that a nonequilibrium phase transition from the Floquet Chern-insulator phase to the Floquet normal-insulator phase takes place accompanied by collapse and vanishing of the Dirac points with the same topological magnetic charges when the angle that the elliptical polarization axis makes with the crystallographic axis is 45$^\circ$. K. Kitayama, M. Ogata, M. Mochizuki, and Y. Tanaka, J. Phys. Soc. Jpn. 91, 104704/1-8 (2021). 題名：Predicted novel type of photoinduced topological phase transition accompanied by collision and collapse of Dirac-cone pair in organic salt α-(BEDT-TTF)2I3

2022.09.12-15
The following presentations have been given by our group members in 2022 JPS Autumn meeting (Tokyo Institute of Technology, Ookayama Campus)

Numb.: 12aW241-1
Title: Theoretical study on the photoinduced topological phases in the ferrimagnetism-induced Dirac electron state
Speakers: Rintaro Eto, M. Mochizuki

Numb.: 13aW331-12
Title: Melting of charge order and topological phase transition in organic conductor α-(BEDT-TTF)₂I₃ irradiated with circularly polarized light
Speakers: Yasuhiro Tanaka, M. Mochizuki

Numb.: 13aW641-2
Title: Theoretical study of magnetic vortex crystals induced by electric dipole interactions
Speakers: Tatsuki Muto, M. Mochizuki

Numb.: 13aW641-5
Title: Theoretical study of magnetic phase transitions and electromagnon excitations in multiferroic CuO
Speakers: Takaaki Iijima, M. Mochizuki

Numb.: 13pW641-2
Title: Theoretical study on creations and manipulations of magnetic skyrmions with the spin-orbit torque
Speakers: Yuto Uwabo, M. Mochizuki

Numb.: 14pW541-6
Title: Theoretical study on the collective spin excitations of quadruple-Q magnetic hedgehog lattices
Speakers: Rintaro Eto, M. Mochizuki

Numb.: 14pW641-7
Title: Theoretical study on thermoelectric effect of magnetic skyrmion crystal confined in a disk-shaped system
Speakers: Junnosuke Matsuki, M. Mochizuki

2022.09.10
The following symposium talk has been given by Mochizuki in the Symposium on ``Spin quantum phenomena driven by light and terahertz" in 2022 JPS Autumn meeting (Tokyo Institute of Technology, Ookayama Campus)

Title: Theory of optical manipulations of magnetisms (10aS2-3)

2022.08.22
Keisuke Kitayama (Former student member) gave an oral presentation at an international workshop ``The 29th International Conference on Low Temperature Physics (LT29)" held at Sapporo Convention Center, Sapporo, Hokkaido, Japan (August 18-24, 2022).

Title: Theoretical studies of photoinduced topological phase transitions in organic salt α-(BEDT-TTF)₂I₃

2022.07.29 The following paper has been published in Physical Review Applied. In this paper, we theoretically demonstrated that spin-waves propagating in a magnetic skyrmion crystal confined in thin-plate magnets have high potential for application to reservoir-computing devices. We numerically examined several characteristics required for reservoir computings for the skyrmion spin-wave reservoir, i.e., the generalization ability, the short-term memory, and the nonlinearlity by imposing the duration estimate task, the short-term memory task, and the parity check task, respectively, and revealed that the skyrmion spin-wave reservoirs possess high figures of merits for these characteristics. This paper was selected as an Editors' Suggestion. M-K. Lee, and M. Mochizuki, Phys. Rev. Applied 18, 014074 (2022).Editors' Suggestion Title: Reservoir Computing with Spin Waves in a Skyrmion Crystal

2022.07.26
A visiting Ph.D student from Ibaraki University, Keisuke Masuda, joined our group. He will stay for a month [Member].

2022.07.21
An article (in Japanese) about our theoretical studies on the photoinduced phase transitions in α-(BEDT-TTF)₂I₃ has been published in Kotaibutsuri journal.

M. Mochizuki, K. Kitayama, Y. Tanaka, M. Ogata
Kotaibutsuri Vol. 57, Issue 7 (2022.07.「Topics」) pp. 1(397)-13(409).

Title: Theoretical studies on the photoinduced topological phase transitions in an organic salt α-(BEDT-TTF)₂I₃

2022.07.21
The following invited talk has been given by Mochizuki in the 12th International Conference on Metamaterials, Photonic Crystals and Plasmonics (META2022, Spain, Torremolinos).

Title: Dynamical Magnetic Phase Transitions in Spin-Charge Coupled Systems

2022.07.18 The following paper has been published in Physical Review Letters. In this paper, we theoretically studied the photoinduced phase transitions in a typical strongly correlated Dirac electron system α-(BEDT-TTF)2I3 irradiated with circularly polarized light. By analyzing an extended Hubbard model with on-site and inter-site Coulomb repulsive interactions using a newly developed theoretical framework which combines real-time dynamics simulations and the Foquet theory, we revealed successive photoinduced phase transitions from the ground-state charge-ordered insulator via the Dirac semimetal to the Chern insulator and its microscopic mechanisms associated with dynamical variations of electronic structures. Y. Tanaka, and M. Mochizuki, Phys. Rev. Lett. 129, 047402/1-6 (2022). Title: Dynamical phase transitions in the photodriven charge-ordered Dirac-electron system

2022.07.13
The following invited talk has been given by Mochizuki in the 24th International Colloquium on Magnetic Films and Surfaces (ICMFS-2022, OIST, Okinawa, Japan).

Title: Dynamical Phenomena of Magnetic Skyrmions

2022.06.28 The following paper has been published in Physical Review Letters. In this paper, we numerically studied low-energy excitations of magnetic skyrmion crystals in the Kondo-lattice model on a triangular lattice with spatial inversion symmetry and discovered two Goldstone modes associated with charge and spin degrees of freedom and their perfect segregation. Our finding indicates that the charges and spins can be excited separately and selectively in the skyrmion crystals stabilized by interactions mediated by conduction electrons in centrosymmetric magnets. R. Eto, R. Pohle, and M. Mochizuki, Phys. Rev. Lett. 129, 017201/1-7 (2022). Title: Low-Energy Excitations of Skyrmion Crystals in a Centrosymmetric Kondo-Lattice Magnet: Decoupled Spin-Charge Excitations and Nonreciprocity

2021.09.17.
Condensed-Matter Theory Seminar (in-person).
Date&Time: 2022.06.17 (Fri.) 14:00
Speaker: Prof. Oleg Tretiakov（(University of New South Wales (UNSW), Sydney)
Title: Nucleation and dynamics of magnetic solitons in topological materials

2022.04.19 The following paper has been published in Physical Review B. In this paper, we theoretically predict a possible photoinduced magnetic phase transition from the ferromagnetism to the 120-degree spin order in the Kondo-lattice model on a triangular lattice. A pseudo half-filled electronic structure turns out to stabilize the 120-degree order, which is realized via electron excitations, dynamical localizations, gap opening, relaxations, and reconstruction of the electronic structure under irradiation with light. This work demonstrates that the light irradiation can induce a noncollinear magnetic state as a nonequilibrium steady phase via the general mechanism. T. Inoue, and M. Mochizuki, Phys. Rev. B 105, 144422 (2022). Photoinduced 120-degree spin order in the Kondo-lattice model on a triangular lattice

2022.03.18
The following symposium talk has been given by Mochizuki in a symbosium of the 77th JPS annual meeting.

Numb.: 18pS11-6
Title: Photoinduced topological phase transitions in the α-type organic salt (Theory)

2021.12.22-23
The following invited talk has been given by Mochizuki in the international conference on "Frustration, Topology and Spin Textures" (Kobe, Japan).

Title: Dynamical manipulations of topological magnetism with light and microwave electromagnetic fields

2021.12.22-23
The following poster presentations has been given by our group in the international workshop on "Frustration, Topology and Spin Textures" (Kobe, Japan).

Title: Theory of optical spin-polarization induction in Rashba spin-orbit electron systems
Presenters: Yasuhiro Tanaka, Takashi Inoue, Masahito Mochizuki

Title: Photoinduced 120-degree spin order and Z₂ vortices in the Kondo-lattice model on a triangular lattice
Presenters: Takashi Inoue, Masahito Mochizuki

Title: Machine learning detection of multiple phase transitions including BKT transition in the q-state clock models
Presenters: Yusuke Miyajima, Masahito Mochizuki

Title: Theoretical Exploration of Magnetism-Induced Negative Thermal Expansion in Honeycomb-Lattice Antiferromagnets
Presenters: Yuto Uwabo, Masahito Mochizuki

Title: Spin and Charge Excitations of Skyrmion Crystals in Itinerant Magnet
Presenters: Rintaro Eto, Rico Pohle, Masahito Mochizuki


2021.12.15
Mochizuki gave an invited talk in RIKEN Institute.

Title: Reservoir computing with spin waves in magnetic skyrmion crystal

2021.12.01-02
Our members, Y. Tanaka, M. Naka, and K. Kitayama, gave presentations in the ISSP workshop on novel materials and phenomena of orgaic compounds (Kashiwa, Japan).

2021.10.30
Rico Pohle has moved to Prof. Motome's group in Univ. of Tokyo.

2021.10.20
The following invited talk has been given by Mochizuki in the international conference on ``Condensed Matter Physics (CONMAT2021)" (online).

Title: Theory of Magnetism-Induced Negative Thermal Expansion in Inverse Perovskite Antiferromagnets

2021.09.27 The following paper has been published in Physical Review B. In this paper, we theoretically predict and reveal possible magnetic-topology switching among skyrmion crystals with different topological numbers and nontopological magnesitms by irradiating centrosymmetric Kondo-lattice magnets on a triangular lattice with circularly polarized microwave magnetic fields. In transient processes of these microwave-induced topology switchings, we observe several distinct behaviors of dynamical phase transitions as well as emergence of peculiar topological magnetisms called meron crystals charcterized by skyrmion numbers of half integers. R. Eto, and M. Mochizuki, Phys. Rev. B 90, 104425 (2021). Title: Dynamical switching of magnetic topology in microwave-driven itinerant magnet

2021.09.24 The following paper has been published in Journal of the Physical Society of Japan. In this paper, we theoretically propose possible realization of the negative thermal expansion in the honeycomb-lattice antiferromagnets composed of edge-sharing MX6 octahedra (M and X represent transition-metal ions and ligand ions, respectively). In contrast to normal materials, crystal volumes of these kinds of magnets are expected to expand upon cooling, which is triggered by the antiferromagnetic phase transition. Y. Uwabo, and M. Mochizuki, J. Phys. Soc. Jpn. 90, 104712 (2021). Title: Proposed Negative Thermal Expansion in Honeycomb-Lattice Antiferromagnets

2021.09.20-23
The following presentations have been given by our members in 2021 JPS Autumn meeting (online)

Numb.: 20aC1-4
Title: Theoreticalstudyonthedynamicsofmagnetictexturesinitineranthelicalmagnets
Speakers: R. Eto, Rico Pohle, M. Mochizuki

Numb.: 21pE1-7
Title: Topological state induced by circularly polarized light in organic conductor
Speakers: Y. Tanaka, M. Mochizuki

Numb.: 22aC1-5
Title: Theoretical Exploration of Negative Thermal Expansion in Honeycomb Lattice Transition Metal Compounds
Speakers: Y. Uwabo, M. Mochizuki

Numb.: 22pL4-3
Title: Detection of the Kosterlitz-Thouless transitions by machine learning
Speakers: Y. Miyajima, Y. Murata, Y. Tanaka, M. Mochizuki

Numb.: 23pH3-5
Title: Theoretical study of the Dirac-point pair annihilation and topological phase transitions in the α-type organic salt induced by elliptically polarized light
Speakers: K. Kitayama, Y. Tanaka, M. Ogata, M. Mochizuki

2021.09.17.
The 5th Condensed-Matter Theory Seminar (online) in FY2021.

Date&Time: 2021.09.17 (Thu.) 16:00
Speaker: Lan Bo (Northeastern University, P. R. China)
Title: Micromagnetic Behaviors of Magnetic Topological Solitons [Abstract]

2021.09.15 The following paper has been published in Journal of the Physical Society of Japan. In this paper, we reveal entire behaviors of photoinduced topological phase transitions in the organic salt α-(BEDT-TTF)2I3 with a pair of tilted Dirac-cone dispersions theoretically using the Floquet thoery. Irradiation by elliptically polarized light give rise to quite rich nonequilibrium phase diagrams containing photoinduced Chern insulator phases. (Selected as Editors' Choice) K. Kitayama, Y. Tanaka, M. Ogata, and M. Mochizuki J. Phys. Soc. Jpn. 90, 104705 (2021).Editors' Choice Title: Floquet theory of photoinduced topological phase transitions in the organic salt α-(BEDT-TTF)2I3 irradiated with elliptically polarized light

2021.08.16 The following paper has been published in Physical Review B. In this paper, we theoretically reveal that irradiation by linearly polarized light can induce a pair annihilation of emergent topological magnetic charges with opposite signs in the momentum space of an organic salt α-(BEDT-TTF)2I3, in which a pair of tilted Dirac-cone bands are slightly gapped due to weak charge dispropotionation. This is a theoretical prediction of monopole-antimonopole pair annihilation of 2D version can be realized by photoirradiation in the momentum space of crystalline materials. K. Kitayama, M. Mochizuki, Y. Tanaka, and M. Ogata Phys. Rev. B 104, 075127 (2021). Title: Predicted photoinduced pair annihilation of emergent magnetic charges in the organic salt α-(BEDT-TTF)2I3 irradiated by linearly polarized light

2021.08.13 The following paper has been published in Physical Review B. In this paper, we theoretically clarify the real-time dynamics of photoinduced topological phase transitions in an organic salt α-(BEDT-TTF)2I3 with tilted Dirac-cone band dispersions under irradiation with circularly polarized light. It is revealed that spatiotemporal dynamics characterized of different three time scales appear, which are, respectively, governed by the light frequency, the averaged magnitude of gaps at the Dirac points, and the difference of gap amplitudes between the two Dirac points under application of an electric field. Y. Tanaka and M. Mochizuki, Phys. Rev. B 104, 085123 (2021). Title: Real-time dynamics of the photoinduced topological state in organic conductor α-(BEDT-TTF)2I3 under continuous-wave and pulse excitations

2021.08.11 The following paper has been published in Physical Review B. In this paper, we demonstrate that a machnie learning is capable of detecting successive Berezinskii-Kosterlizt-Thouless transitions in the n-state clock models. Introducing a new correlation function to the heat-map anlyses, we quantitatively determine the BKT transition points. Y. Miyajima, Y. Murata, Y. Tanaka, and M. Mochizuki, Phys. Rev. B 104, 075114 (2021). Title: Machine learning detection of Berezinskii-Kosterlitz-Thouless transitions in q-state clock models

2021.07.22
The 4th Condensed-Matter Theory Seminar (online) in FY2021.

Date&Time: 2021.07.22 (Thu.) 15:00
Speaker: Rubén M. Otxoa (Hitachi Cambridge Laboratory)
Title: Topological energy release from collision of relativistic antiferromagnetic solitons[Abstract]


2021.07.20
Invited talk in the international conference ``The 11th International Conference on Metamaterials, Photonic Crystals and Plasmonics (META 2021)".

SpeakerM. Mochizuki
Title: Theory of Photoinduced Spin Polarization in Spin-Orbit-Coupled Systems

2021.07.01
Dr. Collins Ashu AKOSA joined our group as a postdoc researcher (project lecturer) of the JST-CREST project.

2021.05.31
Ms. Yoko Takahashi (Secretary) retired.

2021.06.01
The 3rd Condensed-Matter Theory Seminar (online) in FY2021.

Date&Time: 2021.06.01 (Thu.) 16:00
Speaker: Yuya Ominato (KITS, UCAS, P. R. China)
Title: Spin transport phenomena in atomic layer materials [Abstract]


2021.05.26
The 2nd Condensed-Matter Theory Seminar (online) in FY2021.

Date&Time: 2021.05.26 (Wed.) 16:30
Speaker: Atsushi Ono (Tohoku university)
Title: Photoinduced spin-scalar-chiral states in triangular-lattice itinerant magnets [Abstract]


2021.05.25
The 1st KIBAN-A meeting (online).
[Program]

2021.05.24
The 1st Condensed-Matter Theory Seminar (online) in FY2021.

Date&Time: 2021.05.24 (Mon.) 13:30
Speaker: Shunsuke Furuya (Ibaraki university)
Title: DC electric-field controls of superexchange and Dzyaloshinskii-Moriya interactions in Mott insulators [Abstract]


2021.05.18
Rintaro Eto gave a talk on an online seminar in Motome group, Department of Applied Physics, the University of Tokyo.

2021.06.01
The 3rd Condensed-Matter Theory Seminar (online) in FY2021.

Date&Time: 2021.06.01 (Thu.) 16:00
Speaker: Yuya Ominato (KITS, UCAS, P. R. China)
Title: Spin transport phenomena in atomic layer materials [Abstract]


2021.05.26
The 2nd Condensed-Matter Theory Seminar (online) in FY2021.

Date&Time: 2021.05.26 (Wed.) 16:30
Speaker: Atsushi Ono (Tohoku university)
Title: Photoinduced spin-scalar-chiral states in triangular-lattice itinerant magnets [Abstract]


2021.05.25
The 1st KIBAN-A meeting (online). [Program]

2021.05.24
The 1st Condensed-Matter Theory Seminar (online) in FY2021.

Date&Time: 2021.05.24 (Mon.) 13:30
Speaker: Shunsuke Furuya (Ibaraki university)
Title: DC electric-field controls of superexchange and Dzyaloshinskii-Moriya interactions in Mott insulators [Abstract]


2021.05.18
Rintaro Eto (M1 student) gave a talk on an online seminar in Motome group, Department of Applied Physics, the University of Tokyo.