Organization
School of Science Assistant Professor
Title
Assistant Professor
External link
KANEKO SHIN-ICHI
Research Areas
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Natural Science / Magnetism, superconductivity and strongly correlated systems
Papers
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Vortex dynamics in Se-doped ZrTe3
Maegochi S., Miyagawa K., Ienaga K., Kaneko S., Sakata H., Okuma S.
Meeting Abstracts of the Physical Society of Japan 75.1 1516 - 1516 2020
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Thermoelectric response in the field-induced insulating phase of superconducting amorphous MoxGe1-x thin films
Tamoto Y., Ienaga K., Hayashi T., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 75.1 1518 - 1518 2020
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Superconducting fluctuations near the quantum critical point in superconducting amorphous MoxGe1-x thin films
Ienaga K., Hayashi T., Tamoto Y., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 75.1 1486 - 1486 2020
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Effects of the vortex velocity on the reversible-irreversible transition
Miyagawa Kiyoshi, Maegouchi Shun, Kouichiro Ienaga, Shinichi Kaneko, Satoshi Okuma
Meeting Abstracts of the Physical Society of Japan 75.1 1485 - 1485 2020
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Influences of vortex density on the reversible-irreversible transition
Maegochi S., Ienaga K., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 74.2 1328 - 1328 2019
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Thermoelectric effect measurements in disordered two-dimensional superconducting films at very low temperature
Hayashi T., Ienaga K., Okuma S., Kaneko S.
Meeting Abstracts of the Physical Society of Japan 74.1 1666 - 1666 2019
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Clogging in a dc driven vortex system II
Minemura Takahide, Ienaga K., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 74.1 1699 - 1699 2019
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Observation of vortex motion in a plastic-flow regime using scanning tunneling spectroscopy
Murakami A., Tsuchiya K., Ogawa T., Kaneko S., Ienaga K., Sakata H., Okuma S.
Meeting Abstracts of the Physical Society of Japan 74.2 1378 - 1378 2019
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Polycrystalline vortex lattice observed by scanning tunneling spectroscopy
Ogawa T., Tsuchiya K., Kato K., Kaneko S., Ienaga K., Sakata H., Okuma S.
Meeting Abstracts of the Physical Society of Japan 74.1 1667 - 1667 2019
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Observation of vortex motion driven by dc current with scanning tunneling spectroscopy
Tsuchiya K., Ogawa T., Kato K., Kaneko S., Ienaga K., Sakata H., Okuma S.
Meeting Abstracts of the Physical Society of Japan 74.1 1700 - 1700 2019
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Phase diagram of reversible-irreversible transition in a superconducting vortex system
Maegochi S., Nakanishi Y., Ienaga K., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 74.1 1698 - 1698 2019
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Measurements of the vortex Hall effect in FeSe single crystals with pulsed currents
Ienaga K., Takaishi H., Kaneko S., Kasahara S., Matsuda Y., Okuma S.
Meeting Abstracts of the Physical Society of Japan 74.1 1665 - 1665 2019
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Phase diagram of reversible-irreversible transition in a superconducting vortex system II
Miyagawa Kiyoshi, Maegouchi Shun, Ienaga Kouichiro, Kaneko Shinichi, Okuma Satoshi
Meeting Abstracts of the Physical Society of Japan 74.2 1377 - 1377 2019
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Superconducting fluctuations in disordered two-dimensional superconducting films probed by thermoelectric response
Tamoto Yutaka, Ienaga Koichiro, Hayashi Taiko, Kaneko Shinichi, Okuma Satoshi
Meeting Abstracts of the Physical Society of Japan 74.2 1379 - 1379 2019
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Thermoelectric response in the quantum vortex liquid phase of an amorphous superconducting thin film
hayashi T., Ienaga K., Tamoto Y., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 74.2 1329 - 1329 2019
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Topological rectification effect in a magnetic insulator|superconducting vortex system
Lustikova Jana, Saitoh Eiji, Shiomi Yuki, Yokoi Naoto, Kabeya Noriyuki, Kimura Noriaki, Ienaga Koichiro, Kaneko Shin-ichi, Okuma Satoshi, Takahashi Saburo
Meeting Abstracts of the Physical Society of Japan 73 ( 0 ) 670 - 670 2018
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Visualization of vortex motion driven by dc current with scanning tunneling spectroscopy
Ogawa Takashi, Kato Koshiro, Tsuchiya Kazuki, Kaneko S., Ienaga K., Sakata H., Okuma S.
Meeting Abstracts of the Physical Society of Japan 73.2 1108 - 1108 2018
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Time evolution of the vortex configuration associated with dynamic ordering by dc drive II
Maegochi S., Dobroka M., Ienaga K., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 73.2 1106 - 1106 2018
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Visualization of vortex motion with scanning tunneling spectroscopy
Ogawa Takashi, Kato Koshiro, Kaneko S., Ienaga K., Sakata H., Okuma S.
Meeting Abstracts of the Physical Society of Japan 73.1 1674 - 1674 2018
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Detection of vortex liquid state in a superconducting film using Nernst effect measurements
Ienaga K., Arai T., Hayashi T., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 73.2 1109 - 1109 2018
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Change in the vortex configuration by an increase of dc drive
Ienaga K., Dobroka M., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 73.1 1566 - 1566 2018
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Blocking phenomena in a dc driven vortex system II
Minemura Takahide, Ienaga K., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 73.1 1567 - 1567 2018
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Clogging in a dc driven vortex system
Minemura Takahide, Ienaga K., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 73.2 1107 - 1107 2018
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Nernst effect measurements in disordered two-dimensional superconductor at very low temperature
Hayashi Taiko, Ienaga K., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 73.2 1194 - 1194 2018
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Dynamic melting of anisotropy vortex lattice: Velocity dependence
Inoue T., Ochi A., Kawamura Y., Ienaga K., Kaneko S., Kokubo N., Okuma S.
Meeting Abstracts of the Physical Society of Japan 72.1 1625 - 1625 2017
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Effects of anisotropy on random organization of a superconducting vortex system
Ienaga K., Shirahata Y., Dobroka M., Kawamura Y., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 72.1 1626 - 1626 2017
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Change in vortex configuration associated with random organization
Minemura Takahide, Dobroka M., Kaji T., Ienaga K., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 72.1 1700 - 1700 2017
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Measurements of vortex flow in FeSe single crystals with pulsed currents
Takaishi H., Ienaga K., Kaneko S., Kasahara S., Matsuda Y., Okuma S.
Meeting Abstracts of the Physical Society of Japan 72.2 1337 - 1337 2017
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Effects of anisotropy on random organization of a superconducting vortex system II
Shirahata Yudai, Ienaga K., Dobroka M., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 72.2 1345 - 1345 2017
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Observation of vortex motion with Scanning Tunneling Spectroscopy II
Kato Koshiro, Ienaga K., Kaneko S., Sakata H., Okuma S.
Meeting Abstracts of the Physical Society of Japan 72.1 1697 - 1697 2017
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Observation of vortex motion with scanning tunneling spectroscopy III
Kato Koshiro, Kaneko S., Ienaga K., Sakata H., Okuma S.
Meeting Abstracts of the Physical Society of Japan 72.2 1344 - 1344 2017
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Partial reordering of dc plastic flow by a superimposed ac drive
Ienaga K., Dobroka M., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 72.2 1307 - 1307 2017
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21aPS-96 Vortex lattice moving on the conical surface II
Takahashi M., Ienaga K., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 71.1 1718 2016
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Observation of vortex motion with scanning tunneling spectroscopy
Kato Koshiro, Ienaga K., Kaneko S., Sakata H., Okuma S.
Meeting Abstracts of the Physical Society of Japan 71.2 1506 - 1506 2016
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19pAY-2 Transient phenomena of dc driven vortices and dependence on the vortex density III
Kaji T., Kawamura Y., Ienaga K., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 71 1649 - 1649 2016
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19pAY-3 Reversible-Irreversible Transition Seen from a Moving Frame Driven by dc Force II
Minezaki H., Kawamura Y., Ienaga K., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 71 1650 - 1650 2016
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Dynamic Melting of Anisotropy Vortex Lattice III
Inoue Toshiki, Ochi A., Kawamura Y., Ienaga K., Kaneko S., Kokubo N., Okuma S.
Meeting Abstracts of the Physical Society of Japan 71 1439 - 1439 2016
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Effects of anisotropy of vortex lattice on the reversible-irreversible transition
Shirahata Yudai, Kawamura Y., Ienaga K., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 71 1440 - 1440 2016
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Flux flow around the order-disorder transition
Kaji Tetsuya, Kawamura Y., Ienaga K., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 71 1438 - 1438 2016
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24aPS-11 Observation of fast driven vortex-lattice flow and effects of anisotropy
Sohara N., Ochi A., Kaneko S., Kokubo N., Okuma S.
Meeting Abstracts of the Physical Society of Japan 70 1765 - 1765 2015
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17aCS-2 Transient phenomena of dc driven vortices and dependence on vortex density II
Kaji T., Kawamura Y., Moriya S., Murakami E., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 70 1391 - 1391 2015
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21pCT-5 Critical phenomena of the non-equilibrium depinning transition with velocities as a variable
Moriya S., Kawamura Y., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 70 1656 - 1656 2015
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17aCS-1 Dynamic Melting of Anisotropy Vortex Lattices
Ochi A., Kawamura Y., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 70 1390 - 1390 2015
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21pCT-6 Transient phenomena of dc driven vortices and the dependence on the vortex density
Kaji T., Kawamura Y., Moriya S., Murakami E., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 70.1 1657 2015
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17aCS-3 Reversible-irreversible transition seen from a moving frame driven by dc force
Inoue T., Kawamura Y., Nitta R., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 70 1392 - 1392 2015
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17aCS-4 Transient memory in a periodically driven vortex system
Kawamura Y., Kaneko S., Okuma S.
Meeting Abstracts of the Physical Society of Japan 70 1393 - 1393 2015
MISC
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Kibble-Zurek mechanism for the dynamical ordering transition: Effects of asymmetric quench rates
大森康志郎, 前垣内舜, 海老原鯛壱, 家永紘一郎, 家永紘一郎, 金子真一, 大熊哲
日本物理学会講演概要集(CD-ROM) 79 ( 2 ) 2024
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The entropy anomaly in the anomalous metallic states of amorphous superconducting thin films
吉村優輝, 家永紘一郎, 石上貴大, 依田正弘, 金子真一, 大熊哲
日本物理学会講演概要集(CD-ROM) 78 ( 1 ) 2023
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Transverse depinning transition in a superconducting vortex system
前垣内舜, 家永紘一郎, 金子真一, 大熊哲
日本物理学会講演概要集(CD-ROM) 77 ( 1 ) 2022
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Quantum criticality of superconducting amorphous MoxGe1-x thin films probed by thermoelectric response
家永紘一郎, 林太弘, 田本豊嘉, 金子真一, 大熊哲
日本物理学会講演概要集(CD-ROM) 75 ( 2 ) 2020
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Vortex states in Se-doped ZrTe3
前垣内舜, 宮川聖, 家永紘一郎, 金子真一, 小林天, 坂田英明, 大熊哲
日本物理学会講演概要集(CD-ROM) 75 ( 2 ) 2020
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Au/MoxGe1-x薄膜のSTM像と渦糸像
土屋和樹, 小川貴史, 加藤宏志朗, 金子真一, 家永紘一郎, 坂田英明, 大熊哲
日本物理学会講演概要集(CD-ROM) 73 ( 2 ) 2018
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8pBB-2 Depinning and melting in anisotropic vortex lattices
Kawamura Y., Sohara N., Moriya S., Kaneko S., Okuma S.
Meeting abstracts of the Physical Society of Japan 69 ( 2 ) 565 - 565 2014.8
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27pCA-5 Dynamic phase transition of vortex flow probed by relaxation time
Moriya S., Kawamura Y., Kaneko S., Okuma S.
Meeting abstracts of the Physical Society of Japan 69 ( 1 ) 791 - 791 2014.3
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23pQC-5 Scanning Tunneling Spectroscopy of Superconductoring Li_2Pt_3B with non-centrosymmetric crystal structure and strong spin-orbit interaction
Yamasaki Keigo, Suzuki Satoru, Kaneko Shin-ichi, Takeya Hiroyuki, Hirata Kazuto, Nishida Nobuhiko
Meeting abstracts of the Physical Society of Japan 63 ( 2 ) 577 - 577 2008.8
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23pQC-6 Scanning Tunneling Spectroscopy of Superconducting Li_2Pd_3B with Non-Centrosymmetric Crystal Structure
Suzuki S., Yamasaki K., Kanako S., Takeya H., Hirata K., Nishida N.
Meeting abstracts of the Physical Society of Japan 63 ( 2 ) 577 - 577 2008.8
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Scanning Tunneling Spectroscopy of YNi_2B_2C : Vortex Lattice Phase Diagram
Uchiyama K., Nishimori H., Kaneko S., Tokura A., Takeya H., Hirata K., Nishida N.
Meeting abstracts of the Physical Society of Japan 58 ( 2 ) 483 - 483 2003.8
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Scanning Tunneling Spectroscopy of YNi_2B_2C : Quasiparticle States in the Vortex Core
Nishimori H., Uchiyama K., Kaneko S., Tokura A., Takeya H., Hirata K., Nishida N.
Meeting abstracts of the Physical Society of Japan 58 ( 2 ) 483 - 483 2003.8
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Density of states of quasi-particles and symmetry of the Cooper Pairing in YNi_2B_2C
Kaneko S., Aoyagi K., Nishimori H., Tokura A., Takeya H., Nishida N.
Meeting abstracts of the Physical Society of Japan 56 ( 1 ) 484 - 484 2001.3
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LT-STS measurements on magnetic superconductor ErNi_2B_2C
Nishimori H., Kaneko S., Aoyagi K., Tokura A., Nishida N., Takeya H.
Meeting abstracts of the Physical Society of Japan 56 ( 1 ) 484 - 484 2001.3
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Local density of states of quasi-particles around the vortex trapped at a columnar defect in Bi_2Sr_2CaCu_2O_<8+δ>
KAJIWARA H., KANEKO S., SAKATA H., TAGUCHI Y., OSAWA M., NISHIDA N., KAMBARA T., MOCHIKU T., HIRATA K.
Meeting abstracts of the Physical Society of Japan 53 ( 2 ) 686 - 686 1998.9
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Measurements of Temperature Dependence of Tunneling Spectra on Bi_2Sr_2CaCu_2O_x
SAKATA H., KANEKO S., TAGUCHI Y., NISHIDA N., MOCHIKU T., HIRATA K.
Meeting abstracts of the Physical Society of Japan 53 ( 1 ) 531 - 531 1998.3
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Measurements of the Local Density of States of quasi-particles near a Step Edge on Bi_2Sr_2CaCu_2O_x
ONO Y., KANEKO S., SAKATA H., NISHIDA N., MOCHIKU T., HIRATA K.
Meeting abstracts of the Physical Society of Japan 53 ( 1 ) 614 - 614 1998.3
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6p-T-3 Intrinsic Tunneling Spectra on Cleaved Surfaces of Bi_2Sr_2CaCu_2O_<8+δ>
Kaneko S., Nishida N., Mochiku K., Kadowaki K.
Meeting abstracts of the Physical Society of Japan 52 ( 2 ) 639 - 639 1997.9
Presentations
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動的秩序化転移におけるKibble-Zurek機構：非対称クエンチの効果
大森康志郎, 前垣内舜, 海老原鯛壱, 家永紘一郎, 金子真一, 大熊哲
日本物理学会第79回年次大会(2024年次大会) 2024.9
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ハイブリッド型走査トンネル顕微鏡による渦糸プラスチックフロー状態の動的秩序化の観測
金子真一, 大森康志郎, 家永紘一郎, 大熊哲
第30回渦糸物理ワークショップ 2024.12
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アモルファス超伝導薄膜 MoxGe1-x の渦糸相図と次元性
江部薫, 家永紘一郎, 石上貴大, 橘武志, 高野陽向, 金子真一, 大熊哲
第30回渦糸物理ワークショップ 2024.12
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ハイブリッド型走査トンネル顕微鏡による渦糸の動的秩序化測定
金子真一, 大森康志郎, 石井杜和, 家永紘一郎, 坂田英明, 大熊哲
日本物理学会第79回年次大会(2024年次大会) 2024.9
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熱電効果による渦糸系の非平衡相転移の検出
家永紘一郎, 石上貴大, 吉村優輝, 江部薫, 金子真一, 大熊哲
日本物理学会第79回年次大会(2024年次大会) 2024.9
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動的秩序化転移におけるKibble-Zurek機構と臨界現象
大森康志郎, 前垣内舜, 海老原鯛壱, 家永紘一郎, 金子真一, 大熊哲
第30回渦糸物理ワークショップ 2024.12
Research Projects
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Nonequilibrium phase transitions and universality explored by a superconducting vortex system: from rheology to the Kibble-Zurek mechanism
Grant number：25K07200 2025.4 - 2028.3
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
Grant amount：\4420000 （ Direct Cost: \3400000 、 Indirect Cost：\1020000 ）
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Development of precise control and observation of vortex motion and their application to non-equilibrium science
Grant number：15K13516 2015.4 - 2018.3
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research
Okuma Satoshi, KANEKO Shin-ichi
Grant amount：\3770000 （ Direct Cost: \2900000 、 Indirect Cost：\870000 ）
By preparing anisotropic vortex lattices, which cannot be realized in ordinary solids, under an applied field tilted from the normal to the plane of a superconducting film, we study a dynamic-melting phenomenon of the fast driven lattices associated with an increase in the vortex density, using a mode-locking technique. The results show that a melting condition of the anisotropic lattices is determined only by the shorter side of the distorted lattices regardless of the shape of the lattices. In contrast, vortex assemblies with disordered initial configuration become gradually ordered under the application of ac drive. By developing two-step measurements of transient voltage responses, we find that the vortex configuration during the dynamic ordering is separated into disordered and ordered regions and that the ratio of the disordered region increases with the number of cycles.
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Heterogeneous electron correlation in the surface-bulk boundary and across thin layered structures
Grant number：23108004 2011.4 - 2016.3
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)
Kadono Ryosuke, NISHIDA Nobuhiko, HASHIZUME Tomihiro, KOIKE Yoji, INOUE Katsuya, KOJIMA Kenji, KODA Akihiro, ADACHI Tadashi, NAGAOSA Naoto, NAITO Michio, AKIMITSU Jun, FUJIMORI Atsushi, HIRATA Kazuto, TAKEYA Hiroyuki, OKUMA Satoshi, IZAWA Koichi, KANEKO Shin-ichi, MIBU Ko, KISHINE Junichiro, YAMAMOTO Hideki
Grant amount：\205660000 （ Direct Cost: \158200000 、 Indirect Cost：\47460000 ）
While surfaces serves as windows through which materials properties are studied, they exhibit properties often distinct from those as bulk. This points to the possibility that information connecting surface and bulk would help establishing a new science for understanding the state of matter. The ultra slow muon microscope was expected to be the first means to be available for such purpose, and research was planned to study the surface-bulk boundary regions of transition metal oxides and related compounds to seek for relevant information including hints for unprecedented phenomena (heterogeneous electronic correlation). The researches led to the revelation of interesting properties for these compounds in a series of preliminary studies that will be further investigated using the ultra slow muon.
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走査トンネル分光法による充填スクッテルダイト超伝導体の磁束格子の研究
Grant number：18027005 2006 - 2007
日本学術振興会 科学研究費助成事業 特定領域研究
金子 真一, 西田 信彦
Grant amount：\8000000 （ Direct Cost: \8000000 ）
充填スクッテルダイト構造を持つ超伝導体であるPrOs_4Sb_12はその特異な結晶構造に由来した奇妙な超伝導特性を示す。そして超伝導あ発現機構と直接関係ずる超伝導ギャップ関数ぶ異方的であるとの指摘がされている。本研究はPrOs_4Sb_12について走査トンネル顕微鏡/分光法(Scanning Tunneling Microscopy/Spectroscopy:STM/STS)という手法によりその超伝導状態を調べるものである。特に超伝導体内に形成される磁束格子についてSTS法で調べることにより超伝導ギャップ関数についての債報を得ることを目的としている。本年度はPrOs_4Sb_12に磁場を(111)方向にかけた場合について温度0.45KにおけるSTM/STSによる測定を行った。そしで0.2Tから1.4Tまでの磁場範囲でほぼ三角の形状をした磁束格子の測定に成功した。また磁束格子と結晶軸との関係は磁場によって変化しており、結晶軸の対称性を反映していることがわがった。これらの結果ならびに前年度の研究で行った磁場が(001)方向のSTM/STS測定の結果とあわせて、PrOs_4Sb_12における超伝導ギゃップ関数についての考察を行った。これらの測定結果については国内、国外の学会において発表され、現在は投稿論文にまとめているところである。なお本年度の研究では測定の精度向上のために応答速度の早いオシロスコープを購入しノイズへの対策を行った。また実験をするための液体ヘリウムならびに液体窒素の購入のためなどに予算を使用している。
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Studies of Vortex States in Anisotropic Superconductors by Low Temperature Scanning Spectroscopy and Muon Spin Rotation
Grant number：14204035 2002 - 2004
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
NISHIDA Nobuhiko, KANEKO Shin-ichi, HIGEMOTO Wataru
Grant amount：\48230000 （ Direct Cost: \37100000 、 Indirect Cost：\11130000 ）
We have developed low temperature high magnetic field scanning tunneling microscope (LT/HM-STM) and studied the vortex states of anise-tropic superconductors.
(1)Construction of LT/HM-STM : We have constructed two low temperature scanning tunneling microscopes : one is able to be operated in magnetic fields up to 15T at 4.2K and the other, combined with ^3He-^4He dilution refrigerator, I is able to be operated at temperatures down to 0.16K in 6T. We have found that S/N ration of scanning tunneling spectroscopy bu using dilution-refrigerator STM can be greatly improved by modifying the cooling method of the 1.5K stage ; this will help the improvement of LT-STM in the future.
(2)Scanning tunneling spectroscopy of vortex states of anisotropic superconductors in real time and space : The vortex states of YNi2B2C have been studied by Lt-STS/STM at 0.46K. The bound states of the vortex in YNi2B2C have been found by measuring the local density of states of quasi-particles by LT-STS/STM at 0.46K : the fourfold symmetric star-shaped and quantum-regime vortex core have been observed for the first time. This will a breakthrough to microscopic understanding of the vortex states in type-II superconductors. The collective creep of vortices has been successfully observed at temperatures from 6K down to 0.46K in 1T. This is the first visualization of the vortex movement below 1K. Vortex motion in high^temperature superconductors Bi2Sr2CaCu2Ox in 6T at 4.2K was also observed in real time and space. These will open a frontier of research of vortex dynamics including pinning effects in type-II superconductors. By using muon spin rotation anad relaxation method, we ha ve found that the superconducting state of PrOs4Sb12 is time-reversal symmetry breaking. The vortex states of PrOs4b12 have been studied by LT-STS at 0.46K and the results are now in analysis. -
強相関系超伝導体の1K以下における走査トンネル分光
Grant number：12740206 2001 - 2002
日本学術振興会 科学研究費助成事業 奨励研究(A)
金子 真一
Grant amount：\2300000 （ Direct Cost: \2300000 ）
本研究は、強相関系超伝導体の電子状態を調べるために^3Heを用いた走査トンネル顕微鏡を用いて1K以下の低温において走査トンネル分光をおこなうものである。我々の研究グループではこれまでに温度が0.45K、磁場が6Tまでの状況で操作することのできる走査トンネル顕微鏡を開発している。この装置を用い、またロックイン増幅器を用いて精密に微分伝導度を測定することにより強相関系超伝導体の準粒子状態密度を調べた。物質としてはまず昨年度より調べてきたホウ素炭素化合物YNi_2B_2Cにおいて引き続き研究を行った。これまでにこの物質におけるクーパー対の軌道対称性がs波であることをわかってきた。今年度はこの物質における更なる研究からYNi_2B_2Cにおける超伝導エネルギーギャップが非常に異方的であることがわかった。トンネルスペクトルの解析からギャップの大きさで最大のものと最小のものとの比が2.5倍以上もあることが判明した。s波の超伝導体でこのよりな大きな異方性を示すものは、例えば結晶構造の異方性を反映した低次元の電子構造をもつ物質で知られている。しかしYNi_2B_2Cは層状の構造を持ちながらも電子構造は3次元的であるので、この物質において超伝導ギャップの異方性が大きいことは興味をもたれる。なおこの研究結果は国際会議などで発表しており、成果をまとめたものは現在学術雑誌に投稿中である。またその他の物質では、磁性超伝導体である別のホウ素炭素化合物ErNi_2B_2Cや新しく発見されたMgB_2についての走査トンネル分光による研究を行った。
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Studies of Symmetry of Order parameter of non-BCS superconductors by low temperature scanning tunneling microscopy and spectroscopy
Grant number：11304021 1999 - 2001
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
NISHIDA Nobuhiko, MSTSUMOTO Masashige, SAKATA Hideaki, KANEKO Shin-ichi
Grant amount：\6670000 （ Direct Cost: \5800000 、 Indirect Cost：\870000 ）
We have developed low temperature scanning tunneling microscope (LT-STM) with which we are able to perform scanning tunneling spectroscopy (STS) with energy resolution better than 10 μeV with an atomic spatial resolution below 1K in high magnetic fields up to 12 T. At 0.45K the precise STS/STM measurements were able to be performed. Combining our developed STM probe with 3He-4He dilution refrigerator, we are now ready for STS/STM in the temperature region of 0.1K. By using thus developed STS apparatus, we have made STS studies of possible candidates of non-BCS superconductors such as Bi_2Sr_2CaCu_2O_x, YNi_2B_2C, CeRu_2, UPd_2Al_3, CeCoIn_5, Sr_2RuO_4 and MgB_2. In Bi_2Sr_2CaCu_2O_x, YNi_2B_2C, CeRu_2 we have succeeded in observing vortices. The orbital symmetries of Cooper pairing of the superconductors have been studied by LT-STS. In polycrystalline MgB_2 STS measurements were performed from grain to grain and MgB_2 have been found to be a superconductor with 2 energy gaps which can be interpreted in terms of 2-band superconductor. We have indicated that LT-STS/STM is quite a powerful method for superconductivity studies.