博士（工学）, 東京大学

Portable ultrahigh magnetic fields PINK

XFEL

FBG

磁歪

超強磁場

Correlated electron system with multiple orbitals

Exciton condensation

Natural sciences, Magnetism, superconductivity, and strongly correlated systems

Nov. 2021 - Present
文科省卓越研究員

Nov. 2021 - Present
The University of Electro-Communications, Department of Engineering Science, Research Associate

Apr. 2018 - Present
Tokyo Medical and Dental University, College of Liberal Arts and Sciences, Visiting Lecturer

Apr. 2013 - Oct. 2021
University of Tokyo, Institute for Solid State Physics, International MegaGauss Science Laboratory, Research Associate

Apr. 2018 - Mar. 2020
Tohoku University, Institute for Material Research, Visiting Scientist

Aug. 2018 - Aug. 2018
JVSS, Summer School, Lecturer

Apr. 2008 - Mar. 2013
University of Tokyo, Graduate School of Engineering, Department of Applied Physics

Apr. 2006 - Mar. 2008
University of Tokyo, School of Engineering, Department of Mechanical Engineering

Apr. 2004 - Mar. 2006
University of Tokyo, College of Arts and Sciences, Natural Science 1

Apr. 2019 - Mar. 2020
領域3運営委員, 日本物理学会, Society

Apr. 2018 - Mar. 2019
教育委員, 日本真空学会, Society

Apr. 2013 - Mar. 2018
編集員, 日本真空学会, Society

Mar. 2024
Japanese Physical Society of Japan
Discovery of novel electronic phases in LaCoO3 by developing novel strain gauge used at 1000 T
Young Scientist Award of the Physical Society of Japan (Strongly correlated electron systems), Akihiko Ikeda

Nov. 2018
エヌエフ基金
独自開発超高速ひずみ計測装置による極限強磁場中スピン格子科学の開拓
第7回研究開発奨励賞（先端計測）, Akihiko Ikeda

Mar. 2018
Institute for Solid State Physics
「100テスラ領域における新奇スピン状態秩序相の発見と磁歪計測装置の開発」
ISSP Young Scientist Medal, Akihiko Ikeda

Nov. 2017
High magneitc field forum
「メガガウス超強磁場における新奇スピン状態秩序相の発見」
Miura award for young scientist, Akihiko Ikeda

Jun. 2016
Physical Review B
Editors' Suggestion, 池田暁彦

Nov. 2012
第8回放射光表面科学研究部会・顕微ナノ材料科学研究会
Nuclear resonant scattering from physisorbed 83Kr mono-layer
最優秀ポスター賞, Akihiko Ikeda

Nov. 2012
JASRI
「物理吸着クリプトン単原子層のメスバウアー分光：表面電場勾配のプローブとして」
The 5th SPring-8 Budding Researchers Award, Akihiko Ikeda

Dec. 2011
日本表面科学会
「Au(001)上のXe単層・多層吸着層からのレーザー誘起昇脱離：飛行時間分布の層数依存性」
講演奨励賞 スチューデント部門, 池田暁彦

Breathing pyrochlore magnet CuGaCr4S8 : Magnetic, thermodynamic, and dielectric properties
Masaki Gen; Hajime Ishikawa; Atsushi Miyake; Takeshi Yajima; Harald O. Jeschke; Hajime Sagayama; Akihiko Ikeda; Yasuhiro H. Matsuda; Koichi Kindo; Masashi Tokunaga; Yoshimitsu Kohama; Takashi Kurumaji; Yusuke Tokunaga; Taka-hisa Arima
Physical Review Materials, American Physical Society (APS), 7, 10, 16 Oct. 2023, Peer-reviwed
Scientific journal

Signatures of a magnetic superstructure phase induced by ultrahigh magnetic fields in a breathing pyrochlore antiferromagnet
Masaki Gen; Akihiko Ikeda; Kazushi Aoyama; Harald O. Jeschke; Yuto Ishii; Hajime Ishikawa; Takeshi Yajima; Yoshihiko Okamoto; Xuguang Zhou; Daisuke Nakamura; Shojiro Takeyama; Koichi Kindo; Yasuhiro H. Matsuda; Yoshimitsu Kohama
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, 120, 33, 07 Aug. 2023, Peer-reviwed, The mutual coupling of spin and lattice degrees of freedom is ubiquitous in magnetic materials and potentially creates exotic magnetic states in response to the external magnetic field. Particularly, geometrically frustrated magnets serve as a fertile playground for realizing magnetic superstructure phases. Here, we observe an unconventional two-step magnetostructural transition prior to a half-magnetization plateau in a breathing pyrochlore chromium spinel by means of state-of-the-art magnetization and magnetostriction measurements in ultrahigh magnetic fields available up to 600 T. Considering a microscopic magnetoelastic theory, the intermediate-field phase can be assigned to a magnetic superstructure with a three-dimensional periodic array of 3-up-1-down and canted 2-up-2-down spin molecules. We attribute the emergence of the magnetic superstructure to a unique combination of the strong spin–lattice coupling and large breathing anisotropy.
Scientific journal

Gradual Charge Order Melting in Bi0.5Ca0.5MnO3 Induced by Ultrahigh Magnetic Fields
Yuto Ishii; Akihiko Ikeda; Masashi Tokunaga; Koichi Kindo; Akira Matsuo; Yasuhiro H. Matsuda
Journal of the Physical Society of Japan, Physical Society of Japan, 92, 7, 074702, 15 Jul. 2023, Peer-reviwed
Scientific journal

Unveiling new quantum phases in the Shastry-Sutherland compound SrCu2(BO3)2 up to the saturation magnetic field
T. Nomura; P. Corboz; A. Miyata; S. Zherlitsyn; Y. Ishii; Y. Kohama; Y. H. Matsuda; A. Ikeda; C. Zhong; H. Kageyama; F. Mila
Nature Communications, Springer Science and Business Media LLC, 14, 1, 24 Jun. 2023, Peer-reviwed, Abstract

Under magnetic fields, quantum magnets often undergo exotic phase transitions with various kinds of order. The discovery of a sequence of fractional magnetization plateaus in the Shastry-Sutherland compound SrCu₂(BO₃)₂ has played a central role in the high-field research on quantum materials, but so far this system could only be probed up to half the saturation value of the magnetization. Here, we report the first experimental and theoretical investigation of this compound up to the saturation magnetic field of 140 T and beyond. Using ultrasound and magnetostriction techniques combined with extensive tensor-network calculations (iPEPS), several spin-supersolid phases are revealed between the 1/2 plateau and saturation (1/1 plateau). Quite remarkably, the sound velocity of the 1/2 plateau exhibits a drastic decrease of -50%, related to the tetragonal-to-orthorhombic instability of the checkerboard-type magnon crystal. The unveiled nature of this paradigmatic quantum system is a new milestone for exploring exotic quantum states of matter emerging in extreme conditions.
Scientific journal

Magnetic-field-induced valence change in Eu ( Co_1−x_Ni_x )_2_P_2_ up to 60 T
Raito Nakamura; Azumi Ishita; Jin Nakamura; Hiroto Ohta; Yuya Haraguchi; Hiroko Aruga Katori; Hajime Ishikawa; Akira Matsuo; Koichi Kindo; Minoru Nohara; Akihiko Ikeda
Last, Physical Review B, American Physical Society (APS), 107, 23, 235110, 05 Jun. 2023, Peer-reviwed
Scientific journal

Single crystal growths and magnetic properties of hexagonal polar semimetals RAuGe (R = Y, Gd–Tm, and Lu)
Takashi Kurumaji; Masaki Gen; Shunsuke Kitou; Kazuhiko Ikeuchi; Mitsutaka Nakamura; Akihiko Ikeda; Taka-hisa Arima
Journal of Alloys and Compounds, Elsevier BV, 947, 169475-169475, Jun. 2023, Peer-reviwed
Scientific journal

Signature of spin-triplet exciton condensations in LaCoO3 at ultrahigh magnetic fields up to 600 T.
Akihiko Ikeda; Yasuhiro H Matsuda; Keisuke Sato; Yuto Ishii; Hironobu Sawabe; Daisuke Nakamura; Shojiro Takeyama; Joji Nasu
Lead, Nature communications, 14, 1, 1744-1744, 04 Apr. 2023, Peer-reviwed, True, Bose-Einstein condensation of electron-hole pairs, exciton condensation, has been effortfully investigated since predicted 60 years ago. Irrefutable evidence has still been lacking due to experimental difficulties in verifying the condensation of the charge neutral and non-magnetic spin-singlet excitons. Whilst, condensation of spin-triplet excitons is a promising frontier because spin supercurrent and spin-Seebeck effects will be observable. A canonical cobaltite LaCoO3 under very high magnetic fields is a propitious candidate, yet to be verified. Here, we unveil the exotic phase diagram of LaCoO3 up to 600 T generated using the electromagnetic flux compression method and the state-of-the-art magnetostriction gauge. We found the continuous magnetostriction curves and a bending structure, which suggest the emergence of two distinct spin-triplet exciton condensates. By constructing a phenomenological model, we showed that quantum fluctuations of excitons are crucial for the field-induced successive transitions. The spin-triplet exciton condensation in a cobaltite, which is three-dimensional and thermally equilibrated, opens up a novel venue for spintronics technologies with spin-supercurrent such as a spin Josephson junction.
Scientific journal, English

Double dome structure of the Bose–Einstein condensation in diluted S = 3/2 quantum magnets
Yoshito Watanabe; Atsushi Miyake; Masaki Gen; Yuta Mizukami; Kenichiro Hashimoto; Takasada Shibauchi; Akihiko Ikeda; Masashi Tokunaga; Takashi Kurumaji; Yusuke Tokunaga; Taka-hisa Arima
Nature Communications, Springer Science and Business Media LLC, 14, 1, 10 Mar. 2023, Peer-reviwed, Abstract

Bose–Einstein condensation (BEC) in quantum magnets, where bosonic spin excitations condense into ordered ground states, is a realization of BEC in a thermodynamic limit. Although previous magnetic BEC studies have focused on magnets with small spins of S ≤ 1, larger spin systems potentially possess richer physics because of the multiple excitations on a single site level. Here, we show the evolution of the magnetic phase diagram of S = 3/2 quantum magnet Ba₂CoGe₂O₇ when the averaged interaction J is controlled by a dilution of magnetic sites. By partial substitution of Co with nonmagnetic Zn, the magnetic order dome transforms into a double dome structure, which can be explained by three kinds of magnetic BECs with distinct excitations. Furthermore, we show the importance of the randomness effects induced by the quenched disorder: we discuss the relevance of geometrical percolation and Bose/Mott glass physics near the BEC quantum critical point.
Scientific journal

Rhombic skyrmion lattice coupled with orthorhombic structural distortion in EuAl4
Masaki Gen; Rina Takagi; Yoshito Watanabe; Shunsuke Kitou; Hajime Sagayama; Naofumi Matsuyama; Yoshimitsu Kohama; Akihiko Ikeda; Yoshichika Ōnuki; Takashi Kurumaji; Taka-hisa Arima; Shinichiro Seki
Physical Review B, American Physical Society (APS), 107, 2, 25 Jan. 2023, Peer-reviwed
Scientific journal

Magnetic-Field-Induced Insulator Metal Transition of W-doped VO2 Observed by Electromagnetic Flux Compression at ISSP
Yasuhiro H. Matsuda; Yuji Muraoka; Daisuke Nakamura; Akihiko Ikeda; Yuto Ishii; Xu-Guang Zhou; Hironobu Sawabe; Shojiro Takeyama
J. Phys. Soc. Jpn., 91, 10, 101008, 15 Oct. 2022, Peer-reviwed
Scientific journal, English

Anisotropic magnetotransport properties coupled with spiral spin modulation in a magnetic semimetal EuZnGe
Takashi Kurumaji; Masaki Gen; Shunsuke Kitou; Hajime Sagayama; Akihiko Ikeda; Taka-hisa Arima
Physical Review Materials, American Physical Society (APS), 6, 9, 22 Sep. 2022, Peer-reviwed
Scientific journal

Complex magnetic phase diagram with a small phase pocket in a three-dimensional frustrated magnet CuInCr4S8
M. Gen; H. Ishikawa; A. Ikeda; A. Miyake; Z. Yang; Y. Okamoto; M. Mori; K. Takenaka; H. Sagayama; T. Kurumaji; Y. Tokunaga; T. Arima; M. Tokunaga; K. Kindo; Y. H. Matsuda; Y. Kohama
Physical Review Research, American Physical Society (APS), 4, 3, 25 Aug. 2022, Peer-reviwed
Scientific journal

Metastable magnetization plateaus in the S=1 organic spin ladder BIP-TENO induced by a microsecond-pulsed megagauss field
Kazuya Nomura; Yasuhiro H. Matsuda; Akihiko Ikeda; Yoshimitsu Kohama; Hiroshi Tsuda; Naoki Amaya; Toshio Ono; Yuko Hosokoshi
Physical Review B, American Physical Society (APS), 105, 21, 23 Jun. 2022, Peer-reviwed
Scientific journal

Magnetovolume Effect on the First-Order Metamagnetic Transition in UTe₂
Atsushi Miyake; Masaki Gen; Akihiko Ikeda; Kazumasa Miyake; Yusei Shimizu; Yoshiki J. Sato; Dexin Li; Ai Nakamura; Yoshiya Homma; Fuminori Honda; Jacques Flouquet; Masashi Tokunaga; Dai Aoki
Journal of the Physical Society of Japan, Physical Society of Japan, 91, 6, 15 Jun. 2022, Peer-reviwed
Scientific journal

Enhancement of giant magnetoelectric effect in Ni-doped CaBaCo4O7
M. Gen; A. Miyake; H. Yagiuchi; Y. Watanabe; A. Ikeda; Y. H. Matsuda; M. Tokunaga; T. Arima; Y. Tokunaga
Physical Review B, American Physical Society (APS), 105, 21, 09 Jun. 2022, Peer-reviwed
Scientific journal

Closing the hybridization charge gap in the Kondo semiconductor SmB6 with an ultrahigh magnetic field
Daisuke Nakamura; Atsushi Miyake; Akihiko Ikeda; Masashi Tokunaga; Fumitoshi Iga; Yasuhiro H. Matsuda
Physical Review B, American Physical Society (APS), 105, 24, 06 Jun. 2022, Peer-reviwed
Scientific journal

Generating 77 T using a portable pulse magnet for single-shot quantum beam experiments
Akihiko Ikeda; Yasuhiro H. Matsuda; Xuguang Zhou; Shiyue Peng; Yuto Ishii; Takeshi Yajima; Yuya Kubota; Ichiro Inoue; Yuichi Inubushi; Kensuke Tono; Makina Yabashi
Lead, Applied Physics Letters, AIP Publishing, 120, 14, 142403-142403, 04 Apr. 2022, Peer-reviwed, We devised a portable system that generates pulsed high magnetic fields up to 77 T with 3 μs duration. The system employs the single turn coil method, a destructive way of field generation. The system consists of a capacitor of 10.4 μF, a 30 kV charger, a mono air-gap switch, a triggering system, and a magnet clamp, which weighs less than 1.0 tons in total and is transportable. The system offers opportunities for single-shot experiments at ultrahigh magnetic fields in combinations with novel quantum beams. The single-shot x-ray diffraction experiment using a x-ray free-electron laser at 65 T is presented. We comment on the possible update of the system for the generation of 100 T.
Scientific journal

Physical properties of liquid oxygen under ultrahigh magnetic fields
T. Nomura; A. Ikeda; M. Gen; A. Matsuo; K. Kindo; Y. Kohama; Y. H. Matsuda; S. Zherlitsyn; J. Wosnitza; H. Tsuda; T. C. Kobayashi
Physical Review B, American Physical Society (APS), 104, 22, 224423, 20 Dec. 2021, Peer-reviwed
Scientific journal

Phase transition in the 5d1 double perovskite Ba2CaReO6 induced by high magnetic field
Hajime Ishikawa; Daigorou Hirai; Akihiko Ikeda; Masaki Gen; Takeshi Yajima; Akira Matsuo; Yasuhiro H. Matsuda; Zenji Hiroi; Koichi Kindo
Physical Review B, American Physical Society (APS), 104, 17, 174422, 18 Nov. 2021, Peer-reviwed, Magnetic properties of an antiferromagnetic double perovskite oxide Ba2CaReO6, where Re6+ (5d(1)) ions with large spin-orbit coupling are arranged on the face-centered-cubic lattice, are investigated using pulsed high magnetic field up to 66 T. Magnetization and magnetostriction measurements have revealed a magnetic field-induced phase transition at around 50 T. The phase transition accompanies a jump of magnetization and longitudinal magnetostriction of approximately 2x10(-4) with the change of power-law behavior, indicating sizable coupling between the electronic degrees of freedom and the lattice. The high-field phase exhibits a magnetic moment approximately 0.2 mu(B), which is close to the values observed in 5d(1) double perovskite oxides with noncollinear magnetic structure. We argue that Ba2CaReO6 is an antiferromagnet that sits close to the phase boundary between the collinear and noncollinear phases, providing the target material for investigating the interplay between spin-orbital entangled electrons and magnetic field.
Scientific journal, English

Magnetoconduction in the Correlated Semiconductor FeSi in Ultrastrong Magnetic Fields up to a Semiconductor-to-Metal Transition
D. Nakamura; Y. H. Matsuda; A. Ikeda; A. Miyake; M. Tokunaga; S. Takeyama; T. Kanomata
Physical Review Letters, American Physical Society (APS), 127, 15, 06 Oct. 2021, Peer-reviwed
Scientific journal

Field-induced valence fluctuations in YbB12
R. Kurihara; A. Miyake; M. Tokunaga; A. Ikeda; Y. H. Matsuda; A. Miyata; D. I. Gorbunov; T. Nomura; S. Zherlitsyn; J. Wosnitza; F. Iga
Physical Review B, American Physical Society (APS), 103, 11, 03 Mar. 2021, Peer-reviwed
Scientific journal

Higher magnetic-field generation by a mass-loaded single-turn coil
M. Gen; A. Ikeda; S. Kawachi; T. Shitaokoshi; Y. H. Matsuda; Y. Kohama; T. Nomura
Review of Scientific Instruments, AIP Publishing, 92, 3, 033902-033902, 01 Mar. 2021, Peer-reviwed, Single-turn coil (STC) technique is a convenient way to generate ultrahigh magnetic fields of more than 100 T. During the field generation, the STC explosively destructs outward due to the Maxwell stress and Joule heating. Unfortunately, the STC does not work at its full potential because it has already expanded when the maximum magnetic field is reached. Here, we propose an easy way to delay the expansion and increase the maximum field by using a mass-loaded STC. By loading clay on the STC, the field profile drastically changes, and the maximum field increases by 4%. This method offers access to higher magnetic fields for physical property measurements.
Scientific journal

Particle-Hole Symmetry Breaking in a Spin-Dimer System TlCuCl3 Observed at 100 T
X.-G. Zhou; Yuan Yao; Y. H. Matsuda; A. Ikeda; A. Matsuo; K. Kindo; H. Tanaka
Physical Review Letters, American Physical Society (APS), 125, 26, 31 Dec. 2020, Peer-reviwed
Scientific journal

Single shot x-ray diffractometry in SACLA with pulsed magnetic fields up to 16 T
Akihiko Ikeda; Yasuhiro H. Matsuda; Xuguang Zhou; Takeshi Yajima; Yuya Kubota; Kensuke Tono; Makina Yabashi
Lead, PHYSICAL REVIEW RESEARCH, AMER PHYSICAL SOC, 2, 4, Nov. 2020, Peer-reviwed, Single shot x-ray diffraction (XRD) experiments have been performed with an x-ray free electron laser under pulsed high magnetic fields up to 16 T generated with a nondestructive minicoil. The antiferromagnetic insulator phase in a perovskite manganaite, Pr0.6Ca0.4MnO3, is collapsed at a magnetic field of approximate to 8 T with an emergence of the ferromagnetic metallic phase, which is observed via the accompanying lattice changes in a series of the single shot XRD. We discussed the feasibility of the single shot XRD experiment under ultrahigh magnetic fields beyond 100 T, which is generated with a portable destructive pulse magnet.
Scientific journal, English

Two Spin-State Crystallizations in LaCoO3
Akihiko Ikeda; Yasuhiro H. Matsuda; Keisuke Sato
Lead, PHYSICAL REVIEW LETTERS, AMER PHYSICAL SOC, 125, 17, Oct. 2020, Peer-reviwed, We report a magnetostriction study of a perovskite LaCoO3 above 100 T using our state-of-the-art strain gauge to investigate an interplay between electron correlation and spin crossover. There has been a controversy regarding whether two novel phases in LaCoO3 at high magnetic fields result from crystallizations or Bose-Einstein condensation during spin crossover as manifestations of localization and delocalization in spin states, respectively. We show that both phases are crystallizations rather than condensations, and the two crystallizations are different, based on the observations that the two phases exhibit as magnetostriction plateaux with distinct heights. The crystallizations of spin states have emerged manifesting the localizations and interactions in spin crossover with large and cooperative lattice changes.
Scientific journal, English

Magnetic-field-induced insulator-metal transition in W-doped VO2 at 500 T
Yasuhiro H. Matsuda; Daisuke Nakamura; Akihiko Ikeda; Shojiro Takeyama; Yuki Suga; Hayato Nakahara; Yuji Muraoka
NATURE COMMUNICATIONS, NATURE PUBLISHING GROUP, 11, 1, Jul. 2020, Peer-reviwed, Metal-insulator (MI) transitions in correlated electron systems have long been a central and controversial issue in material science. Vanadium dioxide (VO2) exhibits a first-order MI transition at 340 K. For more than half a century, it has been debated whether electron correlation or the structural instability due to dimerised V ions is the more essential driving force behind this MI transition. Here, we show that an ultrahigh magnetic field of 500 T renders the insulator phase of tungsten (W)-doped VO2 metallic. The spin Zeeman effect on the d electrons of the V ions dissociates the dimers in the insulating phase, resulting in the delocalisation of electrons. As the Mott-Hubbard gap essentially does not depend on the spin degree of freedom, the structural instability is likely to be the more essential driving force behind the MI transition.
Scientific journal, English

Direct measurement of resistivity in destructive pulsed magnetic fields
Yoshimitsu Kohama; Fuyuki Nabeshima; Atsutaka Maeda; Akihiko Ikeda; Yasuhiro H. Matsuda
REVIEW OF SCIENTIFIC INSTRUMENTS, AMER INST PHYSICS, 91, 3, 033901-033901, Mar. 2020, Peer-reviwed, True, A simple method for measuring electrical resistivity under destructive pulsed magnetic fields is presented. This method uses pick-up voltage as the power source to allow the measurement of the absolute value of resistivity in ultra-high magnetic fields above 100 T. The experimental setup and its operation are described in detail, and its performance is demonstrated using critical field measurements of thin-film FeSe0.5Te0.5 samples. Possible scientific applications of this setup in high magnetic fields as well as in any other environment with a high field sweep rate are also discussed. Published under license by AIP Publishing.
Scientific journal, English

High magnetic field x-ray diffraction study of the alpha phase of solid oxygen: Absence of giant magnetostriction
Yasuhiro H. Matsuda; Ayumi Shimizu; Akihiko Ikeda; Toshihiro Nomura; Takeshi Yajima; Toshiya Inami; Kohki Takahashi; Tatsuo C. Kobayashi
PHYSICAL REVIEW B, AMER PHYSICAL SOC, 100, 21, Dec. 2019, Peer-reviwed, High magnetic field x-ray diffraction experiments of solid oxygen have been performed at 10 K using DC magnetic fields of up to 5 T as well as pulsed magnetic fields of up to 25 T. The alpha phase of oxygen exhibits no magnetostriction greater than Delta d/d = 10(-4) at 5 T, where d and Delta d denote a lattice plane spacing and its magnetic field variation, respectively. The Delta d/d at higher fields of up to 25 T is found to be smaller than 2x 10(-3). These results contradict the previously reported giant magnetostriction in the alpha phase where the volume magnetostriction Delta V/V reaches 10(-2) at 7.5 T [K. Katsumata et al., J. Phys.: Condens. Matter 17, L235 (2005)].
Scientific journal, English

Magnetoelastic couplings in the deformed kagome quantum spin lattice of volborthite
Akihiko Ikeda; Shunsuke Furukawa; Oleg Janson; Yasuhiro H. Matsuda; Shojiro Takeyama; Takeshi Yajima; Zenji Hiroi; Hajime Ishikawa
PHYSICAL REVIEW B, AMER PHYSICAL SOC, 99, 14, Apr. 2019, Peer-reviwed, Microscopic spin interactions on a deformed kagome lattice of volborthite are investigated through magnetoelastic couplings. A negative longitudinal magnetostriction Delta L/L < 0 in the b axis is observed, which depends on the magnetization M with a peculiar relation of Delta L/L alpha M-1.3. Based on the exchange striction model, it is argued that the negative magnetostriction originates from a pantographlike lattice change of the Cu-O-Cu chain in the b axis, and that the peculiar dependence arises from the local spin correlation. This idea is supported by DFT+U calculations simulating the lattice change and a finite-size calculation of the spin correlation, indicating that the recently proposed coupled-trimer model is a plausible one.
Scientific journal, English

Laboratory Guide : Development of high-speed 100 MHz strain monitor based on fiber Bragg grating technique and observation of spin-lattice couplings at ultrahigh magnetic fields
池田 暁彦; 松田 康弘
Lead, 固体物理, アグネ技術センター, 54, 3, 147-157, Mar. 2019, Peer-reviwed
Japanese

Record indoor magnetic field of 1200 T generated by electromagnetic flux-compression
Nakamura D; Ikeda A; Sawabe H; Matsuda Y. H; Takeyama S
REVIEW OF SCIENTIFIC INSTRUMENTS, 89, 9, Sep. 2018, Peer-reviwed

Note: Optical filter method for high-resolution magnetostriction measurement using fiber Bragg grating under millisecond-pulsed high magnetic fields at cryogenic temperatures
Akihiko Ikeda; Yasuhiro H. Matsuda; Hiroshi Tsuda
REVIEW OF SCIENTIFIC INSTRUMENTS, AMER INST PHYSICS, 89, 9, Sep. 2018, Peer-reviwed, High-resolution magnetostriction measurement of Delta L/L similar to 10(-6) at a speed of 5 MHz is performed using the optical filter method as the detection scheme for the fiber Bragg grating (FBG) based strain monitor under 35-ms pulsed high magnetic fields up to 45 T at 2.2 K. The resolution of magnetostriction is about the same order as the conventionally reported value from FBG based magnetostriction measurement systems for millisecond pulsed magnetic fields. The measurement speed is similar to 100 times the conventional ones. The present system can be a faster alternative for the conventional FBG based magnetostriction measurement system for millisecond pulsed high magnetic fields. Published by AIP Publishing.
Scientific journal, English

Magnetic-Field-Induced Kondo Metal Realized in YbB12
Taku T. Terashima; Yasuhiro H. Matsuda; Yoshimitsu Kohama; Akihiko Ikeda; Akihiro Kondo; Koichi Kindo; Fumitoshi Iga
PHYSICAL REVIEW LETTERS, AMER PHYSICAL SOC, 120, 25, 257206-257206, Jun. 2018, Peer-reviwed, True, The specific heat of the Kondo insulator YbB12 has been measured up to 60 T. The Sommerfeld coefficient y significantly increases at around 50 T, where the insulator metal transition occurs with a steep increase of the magnetization. gamma reaches 67 mJ/(mol K-2) at high fields, which directly indicates that the quasiparticles gain a heavy thermodynamic effective mass and transform into a Kondo metal under magnetic fields. The field-induced Kondo metal has a rather high Kondo temperature around 200 K. The strong Kondo coupling proves that the energy gap collapse does not correspond to the breakdown of the Kondo bound state. The steep increase of the magnetization at the transition manifests the sharp density of states at the Fermi energy formed via the Kondo resonance.
Scientific journal, English

100 MHz high-speed strain monitor using fiber Bragg grating and optical filter applied for magnetostriction measurements of cobaltite at magnetic fields beyond 100 T
Akihiko Ikeda; Toshihiro Nomura; Yasuhiro H. Matsuda; Shuntaro Tani; Yohei Kobayashi; Hiroshi Watanabe; Keisuke Sato
PHYSICA B-CONDENSED MATTER, ELSEVIER SCIENCE BV, 536, 847-849, May 2018, Peer-reviwed, High-speed 100 MHz strain monitor using fiber Bragg grating (FBG) and an optical filter has been devised for the magnetostriction measurements under ultrahigh magnetic fields. The longitudinal magnetostriction of LaCoO3 has been measured at room temperature, 115, 7 and 4.2 K up to the maximum magnetic field of 150 T. The field-induced lattice elongations are observed, which are attributed to the spin-state crossover from the low-spin ground state to excited spin-states.
Scientific journal, English

Crossroad : Shrinking a Coin Using Pulsed High Magnetic Fields
池田 暁彦; 松田 康弘
日本物理学会誌 = Butsuri, 日本物理学会, 73, 5, 318-320, May 2018
Japanese

Magnetostriction studies up to megagauss fields using fiber Bragg grating technique
Akihiko Ikeda; Yasuhiro H. Matsuda; Daisuke Nakamura; Shojiro Takeyama; Hiroshi Tsuda; Kazuya Nomura; Ayumi Shimizu; Akira Matsuo; Toshihiro Nomura; Tatsuo C. Kobayashi; Takeshi Yajima; Hajime Ishikawa; Zenji Hiroi; Masahiko Isobe; Touru Yamauchi; Keisuke Sato
2018 16TH INTERNATIONAL CONFERENCE ON MEGAGAUSS MAGNETIC FIELD GENERATION AND RELATED TOPICS (MEGAGAUSS), IEEE, 98-106, 2018, Peer-reviwed, We here report magnetostriction measurements under pulsed megagauss fields using a high-speed 100 MHz strain monitoring system devised using fiber Bragg grating (FBG) technique with optical filter method. The optical filter method is a detection scheme of the strain of FBG, where the changing Bragg wavelength of the FBG reflection is converted to the intensity of reflected light to enable the 100 MHz measurement. In order to show the usefulness and reliability of the method, we report the measurements for solid oxygen, spin-controlled crystal, and volborthite, a deformed Kagome quantum spin lattice, using static magnetic fields up to 7 T and non-destructive millisecond pulse magnets up to 50 T. Then, we show the application of the method for the magnetostriction measurements of CaV4O9, a two-dimensional antiferromagnet with spin-halves, and LaCoO3, an anomalous spin-crossover oxide, in the megagauss fields.
International conference proceedings, English

Megagauss-field effect on the metal-insulator transition in V(1-x)WxO(2) (x=0.06)
Yasuhiro H. Matsuda; Daisuke Nakamura; Akihiko Ikeda; Shojiro Takeyama; Yuji Muraoka; Yuki Suga
2018 16TH INTERNATIONAL CONFERENCE ON MEGAGAUSS MAGNETIC FIELD GENERATION AND RELATED TOPICS (MEGAGAUSS), IEEE, 107-110, 2018, Peer-reviwed, Effects of ultrahigh magnetic fields on the electronic state of V1-xWxO2 (x=0.06) are investigated. Optical transmission increases with decreasing temperature due to the transformation from the high-temperature metallic state to the low-temperature insulating state. We have made optical transmission measurements with 2 mu m wavelength laser light, and found that the low-temperature insulating state is suppressed by ultrahigh magnetic fields exceeding around 100 T.
International conference proceedings, English

Spin-lattice separation of the spin-ladder compound BIP-TENO by microsecond megagauss field
Kazuya Nomura; Akihiko Ikeda; Yoshimitsu Kohama; Yasuhiro H. Matsuda; Shojiro Takeyama; Naoki Amaya; Toshio Ono; Yuko Hosokoshi
2018 16TH INTERNATIONAL CONFERENCE ON MEGAGAUSS MAGNETIC FIELD GENERATION AND RELATED TOPICS (MEGAGAUSS), IEEE, 150-153, 2018, Peer-reviwed, We have conducted magnetization measurements of the S = 1 spin-ladder compound BIP-TENO using the single-turn coil method which generates micro-second pulsed magnetic field. We observed three magnetization plateaus in the magnetization process up to 100 T. We have also found that the magnetization process depends on the sweep speed of the magnetic fields. Possible origins of this phenomenon are (1) lowering temperature of the samples due to magnetocaloric effect with adiabatic condition realized in the fast (microsecond) pulsed magnetic field, and (2) spin-lattice separation due to a slow response of the magnetostriction whose response time is longer than microsecond range.
International conference proceedings, English

1000 T project of the electro-magnetic flux compression at Kashiwa, UTokyo
Shojiro Takeyama; Daisuke Nakamura; Akihiko Ikeda; Hironobu Sawabe; Yasuhiro H. Matsuda
2018 16TH INTERNATIONAL CONFERENCE ON MEGAGAUSS MAGNETIC FIELD GENERATION AND RELATED TOPICS (MEGAGAUSS), IEEE, 1-4, 2018, Peer-reviwed, The megagauss laboratory, ISSP, UTokyo has a long history of generation of megagauss fields, especially using the electro-magnetic flux compression, originated from the original work in 1970s. We have initiated a new project of 1000 T since 2011, and since then, we have been devoting ourselves to installation of the system and the technical improvements. Condenser bank units with 20 kV, 2 MJ for seed feed coils, and two set of main condenser bank units, 5MJ and 2 MJ each with 50 kV charging capability. The system comprising of those condenser modules has been installed, and operation tuning has been completed. The giant collector plates, and load coil clamping units are installed in anti-explosion chambers. Design of all those instruments was optimized to substantial improvement of the electro-magnetic field energy conversion efficiency. Our recent results of record magnetic field 1200 T obtained from our new megagauss generating systems is presented.
International conference proceedings, English

Contactless ultra-high frequency AC-conductivity measurement applicable to destructive magnets above 100 T
Daisuke Nakamura; Akihiko Ikeda; Yasuhiro H. Matsuda; Shojiro Takeyama
2018 16TH INTERNATIONAL CONFERENCE ON MEGAGAUSS MAGNETIC FIELD GENERATION AND RELATED TOPICS (MEGAGAUSS), IEEE, 45-48, 2018, Peer-reviwed, The contactless high-frequency electrical conductivity measurement using a "self-resonant" probe coil was performed under the ultra-high magnetic fields generated by the destructive magnets, and applied to measure the upper critical field of the cuprate superconductor La1.84Sr0.16CuO4, and also applied to observe a semiconductor-metal transition of the narrow gap semiconductor FeSi.
International conference proceedings, English

High-speed 100 MHz strain monitor using fiber Bragg grating and optical filter for magnetostriction measurements under ultrahigh magnetic fields
Akihiko Ikeda; Toshihiro Nomura; Yasuhiro H. Matsuda; Shuntaro Tani; Yohei Kobayashi; Hiroshi Watanabe; Keisuke Sato
REVIEW OF SCIENTIFIC INSTRUMENTS, AMER INST PHYSICS, 88, 8, Aug. 2017, Peer-reviwed, A high-speed 100 MHz strain monitor using a fiber Bragg grating, an optical filter, and a mode-locked optical fiber laser has been devised, whose resolution is Delta L = L similar to 10(-4). The strain monitor is sufficiently fast and robust for the magnetostriction measurements of materials under ultrahigh magnetic fields generated with destructive pulse magnets, where the sweep rate of the magnetic field is in the range of 10-100 T/mu s. As a working example, the magnetostriction of LaCoO3 was measured at room temperature, 115 K, and 7 similar to 4.2 K up to a maximum magnetic field of 150 T. The smooth dependence on the squared magnetic field and the first-order transition were observed at 115 K and 7 similar to 4.2 K, respectively, reflecting the field-induced spin state evolution. Published by AIP Publishing.
Scientific journal, English

Novel spin-crossover in strongly correlated cobaltite
池田 暁彦; 松田 康弘; 佐藤 桂輔
固体物理, アグネ技術センター, 52, 6, 335-348, Jun. 2017
Japanese

Magnetization Process of the Kondo Insulator YbB12 in Ultrahigh Magnetic Fields
Taku T. Terashima; Akihiko Ikeda; Yasuhiro H. Matsuda; Akihiro Kondo; Koichi Kindo; Fumitoshi Iga
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, PHYSICAL SOC JAPAN, 86, 5, May 2017, Peer-reviwed, The magnetization process of the Kondo insulator YbB12 has been unveiled in ultrahigh magnetic fields of up to 120 T at 4.2 K. We have found a novel metamagnetic transition at B-c2 = 102 T in addition to the previously known transition at B-c1 = 55 T. It has also been observed that the magnetization tends to saturate at around 112 T. Within the rigid band model, the two-energy-gap structure in the density of states (DOS) explains the successive two-step metamagnetism as a result of the Zeeman effect of the DOS. The metamagnetic transition at B-c1 occurs along with an insulator-metal transition and the field-induced phase is expected to be a heavy fermion metallic state. The Kondo effect can weaken at the second transition of B-c2, as theoretically found in the successive two-metamagnetic-transition process in the Kondo semimetal CeNiSn.
Scientific journal, English

Magnetic-field-induced spin crossover of Y-doped Pr0.7Ca0.3CoO3
Akihiko Ikeda; Suyeon Lee; Taku T. Terashima; Yasuhiro H. Matsuda; Masashi Tokunaga; Tomoyuki Naito
PHYSICAL REVIEW B, AMER PHYSICAL SOC, 94, 11, Sep. 2016, Peer-reviwed, The family of hole-doped Pr-based perovskite cobaltites, Pr0.5Ca0.5CoO3 and (Pr1-yREy)(0.3)Ca0.7CoO3 (where RE is rare earth), has recently been found to exhibit simultaneous metal-insulator, spin-state, and valence transitions. We have investigated magnetic-field-induced phase transitions of (Pr1-yYy)(0.7)Ca0.3CoO3 by means of magnetization measurements at 4.2-100 K up to an ultrahigh magnetic field of 140 T with the chemical pressure varied by y = 0.0625, 0.075, 0.1. The observed magnetic-field-induced transitions were found to occur simultaneously with the metal-insulator transitions up to 100 T. The obtained magnetic-field-temperature (B-T) phase diagram and magnetization curves are well analyzed by a spin-crossover model of a single ion with interion interactions. On the other hand, the chemical pressure dependence of the experimentally obtained magnetization change during the phase transition disagrees with the single-ion model when approaching low temperatures. The significant y dependence of the magnetization change at low temperatures may arise from the itinerant magnetism of Co3+ in the paramagnetic metallic phase, where the chemical pressure enhances the exchange splitting by promoting the double-exchange interaction. The observed B-T phase diagrams of (Pr1-yYy)(0.7)Ca0.3CoO3 are quite contrary to that of LaCoO3, indicating that in (Pr1-yYy)(0.7)Ca0.3CoO3 the high-field phase possesses higher entropy than the low-field phase, whereas it is the other way around in LaCoO3.
Scientific journal, English

Spin state ordering of strongly correlating LaCoO3 induced at ultrahigh magnetic fields
Akihiko Ikeda; Toshihiro Nomura; Yasuhiro H. Matsuda; Akira Matsuo; Koichi Kindo; Keisuke Sato
PHYSICAL REVIEW B, AMER PHYSICAL SOC, 93, 22, Jun. 2016, Peer-reviwed, Magnetization measurements of LaCoO3 have been carried out up to 133 T, generated with a destructive pulse magnet at a wide temperature range from 2 to 120 K. A novel magnetic transition was found at B > 100 T and T > T* = 32 +/- 5 K, which is characterized by its transition field increasing with increasing temperature. At T < T*, the previously reported transition at B similar to 65 T was observed. Based on the obtained B-T phase diagram and the Clausius-Clapeyron relation, the entropy of the high-field phase at 80 K is found to be smaller for about 1.5 J K-1 mol(-1) than that of the low-field phase. We suggest that the observed two high-field phases may originate in different spatial orders of the spin states and possibly other degrees of freedom such as orbitals. An inherent strong correlation of spin states among cobalt sites should have triggered the emergence of the ordered phases in LaCoO3 at high magnetic fields.
Scientific journal, English

One-Way Transparency of Light in Multiferroic CuB2O4
S. Toyoda; N. Abe; S. Kimura; Y. H. Matsuda; T. Nomura; A. Ikeda; S. Takeyama; T. Arima
PHYSICAL REVIEW LETTERS, AMER PHYSICAL SOC, 115, 26, Dec. 2015, Peer-reviwed, We experimentally demonstrate one-way transparency of light in multiferroic CuB2O4. The material is rendered transparent for light propagating in one direction, while opaque for light propagating in the opposite direction. The novel transparency results from a destructive interference of the electric dipole and magnetic dipole transitions. The realization of the effect has been accomplished by the application of a high magnetic field and the proper selection of the propagation direction of light in agreement with our quantum mechanical formulation of nonreciprocal directional dichroism.
Scientific journal, English

Nuclear resonant scattering of synchrotron radiation by physisorbed Kr on TiO2(110) surfaces in multilayer and monolayer regimes
Akihiko Ikeda; Taizo Kawauchi; Tatsuo Okano; Katsuyuki Fukutani; Masuaki Matsumoto; Xiao Wei Zhang; Yoshitaka Yoda
PHYSICAL REVIEW B, AMER PHYSICAL SOC, 91, 15, Apr. 2015, Peer-reviwed, Physisorbed Kr layers on TiO2(110) surfaces were investigated by means of nuclear resonant scattering (NRS) of synchrotron radiation at Kr thicknesses ranging from multilayer to monolayer. The NRS intensity was measured as a function of the Kr exposure, from which the NRS signal corresponding to monolayer was estimated as 0.23 cps. The time spectra measured at various thicknesses showed a monotonous decay without any quantum beat features. The recoilless fraction f evaluated from the analysis of the time spectrum revealed a substantial reduction upon temperature rise from 19 to 25 K. As its origin, an order-disorder phase transition of the monolayer Kr is proposed.
Scientific journal, English

Photon stimulated desorption of and nuclear resonant scattering by noble gas atoms at solid surfaces
Akihiko Ikeda
18 Jan. 2015, When a noble gas atom approaches a solid surface, it is adsorbed via the Van

der Waals force, which is called physisorption. In this thesis, several

experimental results concerning physisorbed atoms at surfaces are presented.

First, photon stimulated desorption of Xe atoms from a Au substrate using

nano-second laser is presented. With the time-of-flight measurements, the

translational temperature and the desorption yield of desorbing Xe as a

function of laser fluence are obtained. It is discovered that there are

non-thermal and thermal desorption pathways. It is discussed that the former

path involves a transient formation of the negative ion of Xe. The desorption

flux dependence of the thermal pathway is also investigated. We found that at a

large desorption fluxes the desorption flow is thermalized due to the

post-desorption collisions. The resultant velocity and the temperature of the

flow is found to be in good agreement with the theoretical predictions based on

the Knudsen layer formation. Lastly, nuclear resonant scattering of synchrotron

radiation by the multi- and mono-layer of $^{83}$Kr at a surface of the

titanium oxide is presented. The use of the noble gas atoms as the probes of

the electric field gradient at the solid surfaces is discussed.

Knudsen layer formation in laser induced thermal desorption
Akihiko Ikeda; Masuaki Matsumoto; Shohei Ogura; Tatsuo Okano; Katsuyuki Fukutani
JOURNAL OF CHEMICAL PHYSICS, AMER INST PHYSICS, 138, 12, Mar. 2013, Peer-reviwed, Laser induced thermal desorption of Xe atoms into vacuum from a metal surface following the nano-second pulsed laser heating was investigated by the time-of-flight (TOF) measurement. The desorption flow was studied at a wide range of desorption flux by varying the initially prepared Xe coverage Theta (1 ML = 4.5 x 10(18) atoms/m(2)). At Theta = 0.3 ML, the TOF of Xe was well represented by a Maxwell-Boltzmann velocity distribution, which is in good agreement with thermal desorption followed by collision-free flow. At Theta > 0.3 ML, the peak positions of the TOF spectra were shifted towards the smaller values and became constant at large Theta, which were well fitted with a shifted Maxwell-Boltzmann velocity distribution with a temperature T-D and a stream velocity u. With T-D fixed at 165 K, u was found to increase from 80 to 125 m/s with increasing Theta from 1.2 to 4 ML. At Theta > 4 ML, the value of u becomes constant at 125 m/s. The converging feature of u was found to be consistent with analytical predictions and simulated results based on the Knudsen layer formation theory. We found that the Knudsen layer formation in laser desorption is completed at Knudsen number Kn < 0.39. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4795827]
Scientific journal, English

Photostimulated desorption of Xe from Au(001) surfaces via transient Xe- formation
Akihiko Ikeda; Masuaki Matsumoto; Shohei Ogura; Katsuyuki Fukutani; Tatsuo Okano
PHYSICAL REVIEW B, AMER PHYSICAL SOC, 84, 15, Oct. 2011, Peer-reviwed, Photostimulated desorption (PSD) of Xe atoms from the Au(001) surface in thermal and nonthermal regimes was investigated by the time-of-flight measurement at photon energies of 6.4 and 2.3 eV. Xe was desorbed in a thermal way at high laser fluence, which was in good agreement with theoretical simulations. At a low laser fluence, on the other hand, desorption was induced only at a photon energy of 6.4 eV by a nonthermal one-photon process. We argue that the nonthermal PSD occurs via transient formation of Xe- on Au(001). The lifetime of Xe- is estimated to be similar to 15 fs with a classical model calculation. Whereas the electron affinity of Xe is negative in the isolated state, it is stabilized by the metal proximity effect.
Scientific journal, English

Single crystal growths and physical properties of magnetic polar semimetals RTX (R=Y, Gd-Tm, Lu)
車地崇; 厳正輝; 厳正輝; 鬼頭俊介; 池内和彦; 中村充孝; 池田暁彦; 有馬孝尚; 有馬孝尚
2023, 日本物理学会講演概要集(CD-ROM), 78, 1, 2189-079X, 202302233537255485

Single crystal growth and anisotropic magnetotransport properties of a triangular-lattice helimagnet EuZnGe
車地崇; 厳正輝; 厳正輝; 鬼頭俊介; 佐賀山基; 池田暁彦; 有馬孝尚; 有馬孝尚
2022, 日本物理学会講演概要集(CD-ROM), 77, 2, 2189-079X, 202302233488411757

20pPSB-37 Temperature dependence of the magnetization of Kondo semiconductor YbB_<12> and the gap structure
Terashima T. T.; Ikeda A.; Matsuda Y. H.; Takeyama S.; Kondo A.; Kindo K.; Iga F.
The Physical Society of Japan (JPS), 2016, Meeting Abstracts of the Physical Society of Japan, 71, 2140-2140, Japanese, 2189-079X, 110010058095, AA12721570

22aPS-24 Magnetization measurements of valence fluctuating system EuNi_2X_2 (X = Si_<1-x>Ge_x, P) in ultra-high magnetic field over 100 T
Ichikawa T.; Ikeda A.; Matsuda Y. H.; Mitsuda A.; Wada H.
The Physical Society of Japan (JPS), 2016, Meeting Abstracts of the Physical Society of Japan, 71, 2418-2418, Japanese, 2189-079X, 110010058357, AA12721570

19pBM-9 Spin state ordering in LaCoO_3 above 100 T
Ikeda A.; Nomura T.; Matsuda Y. H.; Matsuo A.; Kindo K.; Sato K.
The Physical Society of Japan (JPS), 2016, Meeting Abstracts of the Physical Society of Japan, 71, 2027-2027, Japanese, 2189-079X, 110010057992, AA12721570

19pDC-4 Temperature dependence of the high-_eld induced spin-state transitions in (Pr_<1-y>Y_y)_<0:7>Ca_<0:3>CoO_3 (y=0:075; 0:1)
Ikeda A.; Lee S.; Matsuda Y. H.; Takeyama S.; Kindo K.; Naito T.
The Physical Society of Japan (JPS), 2015, Meeting Abstracts of the Physical Society of Japan, 70, 2209-2209, Japanese, 2189-079X, 110010029803, AA12721570

18aDA-10 Saturation behavior of magnetization of Kondo semiconductor YbB_<12> at high magnetic fields beyond 100 T
Terashima T. T.; Ikeda A.; Matsuda Y. H.; Takeyama S.; Kondo A.; Kindo K.; Iga F.
The Physical Society of Japan (JPS), 2015, Meeting Abstracts of the Physical Society of Japan, 70, 1984-1984, Japanese, 2189-079X, 110010029582, AA12721570

Nuclear resonant scattering of synchrotron radiation by 83Kr on TiO2
Ikeda Akihiko; Kawauchi Taizo; Matsumoto Masuaki; Okano Tatsuo; Fukutani Katsuyuki; Zhang Xiao Wei; Yoda Yoshitaka
放射光の特性である波長可変性，集光性，高輝度を活かすことで，Kr表面吸着層を試料としたメスバウアー分光を行った．実験では超高真空中に担持したTiO2(001)基板を20Kまで冷却した．試料としてKrの単層・多層吸着層を作成した．SPring-8 BL09XUにて実験を行った．本実験で初めて，単層吸着層からの信号を0.1Hz程度で取得できることを示した．多層・単層でのスペクトル形状の相違を議論する．, The Surface Science Society of Japan, 2012, Abstract of annual meeting of the Surface Science of Japan, 32, 184-184, 130005456590

The Surface Science Society of Japan (eds) Compendium of Surface and Interface Analysis
Akihiko Ikeda; Katsuyuki Fukutani
Joint work, Photo-stimulated desorption (p487-p492), Springer, Feb. 2018

Novel phases of LaCoO3 at 600 T
Akihiko Ikeda
Invited oral presentation, English, 日本物理学会, Invited
20 Mar. 2024
18 Mar. 2024- 21 Mar. 2024

Road to XFEL experiments on condensed matters at above 100 Tesla
Akihiko Ikeda
Invited oral presentation, English, Japan Physical Society meeting, Invited
19 Mar. 2024
18 Mar. 2024- 21 Mar. 2024

Using mini-coil and mini-bank in plasma experiments, and the possibility of 100 T plasma experiment
Akihiko Ikeda
Invited oral presentation, English, Matter in Extreme Conditions for MAgneTized PLAsmas (MECMATPLA), Invited, Peer-reviewed
07 Feb. 2024
05 Feb. 2024- 09 Feb. 2024

Road to X-ray science at 100 T
Akihiko Ikeda
Invited oral presentation, English, Frontiers of Synchrotron and XFEL Research at High Magnetic Field (MagX), Invited
09 Nov. 2023
08 Nov. 2023- 10 Nov. 2023

Quest for the investigation of spin-lattice couplings of matter at ultrahigh magnetic fields up to 600 T
Akihiko Ikeda
Invited oral presentation, English, The 15th Asia Pacific Physics Conference (APPC15), Invited
25 Aug. 2022
21 Aug. 2022- 26 Aug. 2022

Spin triplet exciton condensations in LaCoO3 at ultrahigh magnetic fields up to 600 T
Akihiko Ikeda
Invited oral presentation, English, the 29th International Conference on Low Temperature Physics (LT29), Invited
18 Aug. 2022
18 Aug. 2022- 24 Aug. 2022

Investigation of quantum phenomena of materials at well above 100 T by means of next generation quantum beams
JST FOREST, Principal investigator
Apr. 2023 - Mar. 2030

Promotion of the 1000-Tesla science
松田 康弘; 大和田 謙二; 池田 暁彦; 徳永 将史; 木村 尚次郎; 稲田 聡明; 岡 隆史; 伏屋 雄紀; 那須 譲治; 富田 裕介; 笠松 秀輔
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, The University of Tokyo, Grant-in-Aid for Transformative Research Areas (A), 23H04859
01 Apr. 2023 - 31 Mar. 2028

Investigation of spin-lattice couplins in strongly correlated condensed matters at 1000 T
池田 暁彦; 野村 肇宏; 米澤 進吾; 野原 実; 大池 広志
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, The University of Electro-Communications, Grant-in-Aid for Transformative Research Areas (A), 23H04861
01 Apr. 2023 - 31 Mar. 2028

状態密度変化によるゼロヒステリスの巨大磁気熱量効果の実現に向けたメカニズム解明
木原 工; XU XIAO; 池田 暁彦
日本学術振興会, 科学研究費助成事業, 岡山大学, 基盤研究(B), 23H01672
01 Apr. 2023 - 31 Mar. 2026

Microscopic investigation of crystal structures at 100 Tesla using novel quantum beams
池田 暁彦
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, The University of Electro-Communications, Grant-in-Aid for Scientific Research (B), 23H01121
01 Apr. 2023 - 31 Mar. 2026

先端量子ビームによる物質の極限環境量子状態の解明
池田暁彦
文科省卓越研究員
Nov. 2021 - Mar. 2025

ポータブルパルス超強磁場発生装置 PINK による XFEL-100 テスラ共用実験
池田暁彦
SACLA/SPring-8基盤開発プログラム
Apr. 2021 - Mar. 2024

Study of the spin-lattice coupling using a single-shot x-ray measurement in ultrahigh magnetic fields
松田 康弘; 池田 暁彦; 久保田 雄也
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, The University of Tokyo, Grant-in-Aid for Challenging Research (Pioneering), X線は物質の構造や電子状態を微視的に明らかにする優れたプローブであり、磁場中で起こる様々な量子現象を理解するために、強磁場環境下でのX線実験技術 の開発は興味深く重要である。世界的に放射光X線とパルス強磁場を組み合わせて40テスラの実験が可能となっているが、現状の技術の延長では磁場の上限は50 テスラ程度にとどまる。マイクロ秒の超高速磁場を用いれば100テスラ以上の超強磁場X線実験が可能となるが、X線の光源もシングルショットで十分な強度を有する自由電子レーザー(XFEL)を用いることが必須となる。本年度、パルス超強磁場発生可能となるシステムを構築し、実際にその装置を用いたXFEL実験を兵庫県の自由電子レーザー施設SACLAにて2021年5月25~28日(課題番号2021A8063)および、2022年2月22~25日(課題番号2021B8064)で行った。最大77テスラの磁場を安全に発生し、実際にその下でX線回折計測に成功したことで、X線回折実験の世界記録を大きく上回ることができた。2021年5月の実験では、Mn酸化物BiCa0.5Mn0.5O3における磁場誘起電荷秩序融解に伴う構造相転移をX線回折でとらえ、結果はApplied Physics Letter誌に論文掲載された。BiCa0.5Mn0.5O3は、これまでに50テスラ付近で相転移が起こることが予想されていたが、実際に結晶構造の変化を確かめることはできていなかった。さらに、この物質は低温では相転移の動的挙動が緩慢になる傾向が磁化測定からわかっており、結晶格子変形との関連は今後興味深い研究テーマである。また、2022年2月には(Pr,Y)CaCoO3における磁場中X線回折実験を低温で行い、Prの価数転移とCoのスピン転移による構造相転移の観点から現在結果を解析・考察中である。, 20K20521
30 Jul. 2020 - 31 Mar. 2023

プラセオジウム系コバルト酸化物における磁気超流動性の検証
加藤科学振興会, Principal investigator
Apr. 2022 - Mar. 2023

磁気ひずみの精密計測による磁気の超流動・常流動転移の探索
池谷科学技術振興財団, Principal investigator
Apr. 2022 - Mar. 2023

超高精度2軸回転磁歪計測システムによる回転対称性の破れた磁気状態の探索
精密測定技術振興財団, 研究助成, 電気通信大学, Principal investigator
Apr. 2022 - Mar. 2023

Superfluidity at room temperature realized by magnetic field
Akihiko Ikeda
TEPCO Memorial Foundation, Research Grant (Basic Research), University of Tokyo, Principal investigator
Apr. 2019 - Mar. 2022

Investigation of Bose-Einstein condensation of triplet exciton in cobaltites
Ikeda Akihiko
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, The University of Tokyo, Grant-in-Aid for Early-Career Scientists, We have carried out a study to clarify the origin of the high-magnetic field induced phases of LaCoO3. It has been found that there are two novel phases up above 100 T region. The candidate for the novel phases are the crystallizations of spin-state degree of freedom (SSC: Spin-state crystal) and the Bose-Einstein condensation of spin-state degree of freedom (EC: Excitonic condensation). We have developed a magnetostriction measurement system for up above 100 T region utilizing the fiber Bragg grating strain gauge and implementing a very high-speed 100 Mhz detection system. We carried out a series of magnetostriction measurement of LaCoO3. We observed magnetostriction plateaux for both of the two novel phases. We concluded that the two novel phases are both originating in SSCs rather than EC., 18K13493
01 Apr. 2018 - 31 Mar. 2020

Investigation of spin state crystallization in a cobaltite
Ikeda Akihiko; Matsuda Yasuhiro H.; Sato Keisuke
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, The University of Tokyo, Grant-in-Aid for Young Scientists (B), Principal investigator, In this research project, we have investigated a long standing problem of the spin-crossover of a cobaltite. Previous studies have focused on its temperature evolution, whereas we have applied a new axis of ultrahigh-magnetic fields along with the temperature evolution. We have explored in a wide range of temperature and magnetic field, resulting in a discovery of anomalous spin-state ordered phases above 100 T. The study opens a new area of multi-orbital Mott physics., 16K17738
01 Apr. 2016 - 31 Mar. 2019