Publications

Preprint

 

Imaging Josephson Vortices on Curved Junctions

Y. Fujisawa, A. Krishnadas, B. Smith, M. Pardo-Almanza, H. Hiyane, Y. Nagai, T. Machida, Y. Okada

arxiv:2307.11970

Imaging emergent exotic quasiparticle state in a frustrated transition metal oxide

Y. Fujisawa, A. Krishnadas, C. H. Hsu, T. Takeda, S. Liu, M. P. Almanza, Y. Obata, D. van Dinter,
K. Yamagami, G. Chang, M. Kobayashi, C. Y. Kuo, Y. Okada

arXiv:2306.06708

Visualizing magnetic field-induced rotational electronic symmetry breaking in a spinel oxide superconductor

Y. Fujisawa, A. Krishnadas, C. H. Hsu, B. Smith, M. P. Almanza, Y. Obata, D. van Dinter, G. Chang,
 Y. Nagai, T. Machida, Y. Okada

arXiv:2306.06711  

Publication

Magnetotransport properties in van-der-Waals RTe3 (R = La, Ce, Tb)

T. Higashihara, R. Asama, R. Nakamura, M. Watanabe, N. Tomoda,
T. J. Hasiweder, Y. Fujisawa, Y. Okada, T. Iwasaki, K. Watanabe, T. Taniguchi, N. Jiang, and Y. Niimi

[Editor's Suggestion]

Physical Rev. B 109, 134404 (2024)

 

Widely tunable Berry curvature in the Magnetic Semimetal Cr1+dTe2

Y. Fujisawa, M. Pardo-Almanza, C. H. Hsu, A. Mohamed, K. Yamagami, A. Krishnadas, F. C. Chuang, K. H. Khoo, J. Zang, A. Soumyanarayanan, Y. Okada

Adv. Mater. 2207121(2023) 

 

Enhancement of spin–flop-induced magnetic hysteresis in van der Waals magnet (Fe1-xCox)5GeTe2

T Ohta, K. Kurokawa, N. Jiang, K. Yamagami, Y. Okada, and Y. Niimi

Appl. Phys. Lett. 122, 152402 (2023)

Visualization of robust two-dimensional bulk states with suppressed surface state on epitaxial PdCoO2 thin films with bipolar surfaces

T. Kawamoto, A. Krishnadas, C. H. Hsu, M. Pardo-Almanza,
Y. Fujisawa, G. Chang, T. Harada, Y. Okada

Phys. Rev. Materials 7, 024001 (2023) 

Controlling inversion disorder in a stoichiometric spinel magnet

Margarita G. Dronova, Feng Ye, Scott E. Cooper, Anjana Krishnadas, Christina M. Hoffmann, Yuita Fujisawa,
Yoshinori Okada, Daniel I. Khomskii, Yejun Feng

PNAS 119, e2208748119 (2022)

Large antiferromagnetic fluctuation enhancement of the thermopower at a critical doping in magnetic semimetal Cr1+dTe2

M. Atwa, Y. Fujisawa, T. Onishi, M. Pardo-Almanza, M. Couillard, K. Harada, T. Takeuch, Y. Okada

Phys. Rev. B 106, 155112 (2022)

Anomalous Magnetic Moment Direction under Magnetic Anisotropy Originated from Crystalline Electric Field
in van der Waals Compounds CeTe3 and CeTe2Se

D. Ueta, R. Kobayashi, H. Sawada, Y. Iwata, S. Yano, S. Kuniyoshi, Y. Fujisawa, T. Masuda, Y. Okada, and S. Itoh
J. Phys. Soc. Jpn. 91, 094706 (2022)

 

Metallic delafossite thin films for unique device applications

T. Harada and Y. Okada

[FEATURED]  APL Materials 10, 070902 (2022)

Enhanced d–p hybridization intertwined with anomalous ground state formation in van der Waals-coupled magnetic metal Fe5GeTe2

K. Yamagami, Y. Fujisawa, M. Pardo-Almanza, B. R. M. Smith, K. Sumida, Y. Takeda, and Y. Okada

Phys. Rev. B 106, 045137 (2022)

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Observation of near EF Fermi-arc van Hove singularity with prominent coupling to phonon in a van der Waals coupled Weyl semimetal

Z. Wang, C. Y. Huang, C. H. Hsu, H. Namiki, T. R. Chang, F. C. Chuang, H. Lin, T. Sasagawa, V. Madhavan, and Y. Okada

Phys. Rev. B 105, 075110 (2022)

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Magnetic frustration in a van der Waals metal CeSiI

R. Okuma, C. Ritter, G. J. Nilsen, Y. Okada

Phys. Rev. Materials (L) 5, L121401 (2021)

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Visualizing superconductivity in an inversion-symmetry- broken doped Weyl semimetal

Z. Wang, J. Olivares, H. Namiki, V. Pareek, K. Dani, T. Sasagawa, V. Madhavan and Y. Okada

Phys. Rev. B 104, 115102 (2021)

Itinerant ferromagnetism mediated by giant spin polarization of metallic ligand band in van der Waals magnet Fe5GeTe2

K. Yamagami, Y. Fujisawa, B. Driesen, C. H. Hsu, K. Kawaguchi, H. Tanaka, T. Kondo, Y. Zhang, H. Wadati, K. Araki, T. Takeda, Y. Takeda, T. Muro, F. C. Chuang, Y. Niimi, K. Kuroda, M. Kobayashi, Y. Okada

     Phys. Rev. B (L) 103, L060403 (2021)

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Single Molecular Adsorption of Terbium(III) Bis-phthalocyaninato (TbPc2) Governed by Two Surface Reconstructions of Perovskite Type SrVO3 Epitaxial Ultrathin Film
Hirofumi Oka, Keiichi Katoh, Yoshinori Okada, Daichi Oka, Taro Hitosugi, Masahiro Yamashita, and Tomoteru Fukumura
Chem. Lett., 50, 1489 (2021)

Butterfly-shaped magnetoresistance in van der Waals ferromagnet Fe5GeTe2 
T. Ohta, M. Tokuda, S. Iwakiri, K. Sakai, B. Driesen, Y. Okada, K. Kobayashi, and Y. Niimi

AIP Advances 11, 025014 (2021)

Shubnikov-de-Haas oscillation and possible modification of effective mass in CeTe3 thin films
M. Watanabe, R. Nakamura, S. Lee, T. Asano, T. Ibe, M. Tokuda,
H. Taniguchi, D. Ueta, Y. Okada, K. Kobayashi, and Y. Niimi

 AIP Advances 11, 015005 (2021) 

Tailoring Magnetism in Self-intercalated Cr1+δTe2 Epitaxial Films

Y. Fujisawa, M. Pardo-Almanza, J. Garland, K. Yamagami, X. Zhu, X. Chen, K. Araki, T. Takeda, M. Kobayashi, Y. Takeda, C. H. Hsu, F. C. Chuang, R. Laskowski, K. H. Khoo, A. Soumyanarayanan, and Y. Okada

Phys. Rev. Materialls 4, 114001 (2020)

Fermionic Order by Disorder in a van der Waals Antiferromagnet

R. Okuma, D. Ueta, S. Kuniyoshi, Y. Fujisawa, B. Smith, C. H. Hsu, Y. Inagaki, W. Si, T. Kawae, H. Lin, F. C. Chuang, T. Masuda, R. Kobayashi, Y. Okada

Scientific Reports 10, 15311 (2020)

Quantum oscillations with magnetic hysteresis observed in CeTe3 thin films

M. Watanabe, S. Lee, T. Asano, T. Ibe, M. Tokuda, H. Taniguchi, D. Ueta, Y. Okada, K. Kobayashi, and Y. Niimi

Appl. Phys. Lett. 117, 072403 (2020)
 

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Enhancement of coercive field in atomically-thin quenched Fe5GeTe2

T. Ohta, K. Sakai, H. Taniguchi, B. Driesen, Y. Okada, K. Kobayashi and Y. Niimi

Appl. Phys. Express 13, 043005 (2020)

 

Three-dimensional electronic structure in ferromagnetic Fe3Sn2 with breathing kagome bilayers

H. Tanaka, Y. Fujisawa, K. Kuroda, R. Noguchi, S. Sakuragi, C. Bareille, B. Smith, C. Cacho, S. W. Jung, T. Muro, Y. Okada, and T. Kondo

Phys. Rev. B 101, 161114(R) (2020)
 

 

Top-down Approach using Supercritical Carbon Dioxide Ball Milling for Producing Sub-10 nm scaled Bi2Te3 Powders

M. Atwa, T. Nakagawa, A. Yonamine, D. C. Lloyd, M. Schreiber, K. Miyazaki, T. Takeuchi and Y. Okada

Applied Physics Express 13 067002 (2020)

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Width-induced metal-insulator transition in SrVO3 lateral nanowires spontaneously formed on the ultrathin film

H. Oka, Y. Okada, K. Kaminaga, D. Oka, T. Hitosugi, and T. Fukumura

Applied Physics Letters 117, 051603(2020)

 

Two distinct surface terminations of SrVO3 (001) ultrathin films as an influential factor on metallicity

H. Oka, Y. Okada, T. Hitosugi, and T. Fukumura

Appl. Phys. Lett. 113, 171601 (2018)

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Disorder induced power-law gaps in an Insulator-Metal Mott transition

Z. Wang, Y. Okada, J. O’ Neal, W. Zhou, D. Walkup, C. Dhital, T. Hogan, P. Clancy, Y. J. Kim, Y. F. Hu, L. Santos, S. D. Wilson, N, Trivedi and V. Madhavan

PNAS 115, 11198 (2018)

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Anisotropic Band Splitting in Monolayer NbSe2: Implications for Superconductivity and Charge Density Wave

Y. Nakata, K. Sugawara, S. Ichinokura, Y. Okada, T. Hitosugi, T. Koretsune, K. Ueno, S. Hasegawa, T. Takahashi, and T. Sato,

npj 2D Materials and Applicationsvolume 2, 12 (2018)

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Atomic-scale visualization of oxide thin-film surfaces

K. Iwaya, T. Ohsawa, R. Shimizu, Y. Okada, and T. Hitosugi

Sci Technol Adv Mater. 19(1): 282–290 (2018).
 

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Scanning tunneling spectroscopy of superconductivity on surfaces of LiTi2O4(111) thin films

Y. Okada, Y. Ando, R. Shimizu, E. Minamitani, S. Shiraki, S. Watanabe, and T. Hitosugi

Nature Communications 8, 15975 (2017)

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Quasiparticle interference on cubic perovskite oxide surfaces

Y. Okada, T. R. Chang, G. Chang, R. Shimizu, H. T. Jeng, S. Shiraki, A. Bansil, H. Lin, T. Hitosugi

Phys. Rev. Lett. 119, 086801 (2017)

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Monolayer 1T-NbSe2 as a Mott insulator

Y. Nakata, K. Sugawara, R. Shimizu, Y. Okada, P. Han, T. Hitosugi, K. Ueno, T. Sato, and T. Takahashi

NPG Asia Materials 8, e321 (2016)

 

 

Nanoscale determination of the mass enhancement factor in the lightly doped bulk insulator ​lead selenide

I. Zeljkovic, K. L. Scipioni, D. Walkup, Y. Okada, Wenwen Zhou, R. Sankar, G. Chang,Y. J. Wang, H. Lin, A. Bansil, F. Chou, Z. Wang and V. Madhavan

Nature Communication 6, 6559-6563 (2015)

 

 

Dirac mass generation from crystal symmetry breaking on the surfaces of topological crystalline insulators

I. Zeljkovic★, Y. Okada★, C. Y. Huang, R. Sankar, D. Walkup, W. Zhou, M. Serbyn, F. Chou, W. F. Tsai, H. Lin, A. Bansil, L. Fu, M. Z. Hasan, V. Madhavan

Nature Materials 14, 318–324 (2015)

 

 

Mapping the unconventional orbital texture in topological crystalline insulators

I. Zeljkovic★, Y. Okada★, C. Y. Huang, R. Sankar, D. Walkup, W. Zhou, M. Serbyn, F. Chou, W. F. Tsai, H. Lin, A. Bansil, L. Fu, M. Z. Hasan, V. Madhavan

Nature Physics 10, 572-577 (2014)

 

 

Electronic phase separation in the doped spin-orbit driven Mott phase of Sr3(Ir1-xRux)2O7

C. Dhital, T. Hogan, W. Zhou, X. Chen, Z. Ren, M. Pokharel, Y. Okada, M. Heine, W Tian, Z. Yamani, C. Opeil, J. S. Helton, J. W. Lynn, Z. Wang, V. Madhavan, S. D. Wilson

Nature Communications 5, 3377 (2014)

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Observation of Dirac node formation and mass acquisition in a topological crystalline insulator

Y. Okada, M. Serbyn, H. Lin, D. Walkup, W. Zhou, C. Dhital, M. Neupane, S. Xu, Y. J. Wang, R. Sankar, F. Chou, A. Bansil, Z. Hasan, S. D. Wilson, L. Fu and Vidya Madhavan

Science 341, 1496-1499 (2013)

 

 

 

Topological insulators: Plasmons at the surface

Yoshinori Okada, Vidya Madhavan

 Nature Nanotechnologies 8, 541-542 (2013)

 

 

Topological dangling bonds with large spin splitting on the surfaces of Bi2Se3

Hsin Lin, T. Das, Y. Okada, M. C. Boyer, W. D. Wise, M. Tomasik, B. Zhen, E. Hudson, W. Zhou, V. Madhavan, C. Y. Ren, H. Ikuta, and A. Bansil1

Nano Letters, 13, 1915–1919. (2013)

 

Imaging the evolution of metallic states in a spin-orbit interaction driven correlated iridate

Y. Okada, D. Walkup, H. Lin, C. Dhital, T. R. Chang, S. Khadka, W. Zhou, H. T. Jeng, A. Bansil, Z. Wang, S. Wilson, V. Madhavan

 Nature Materials 12, 707-713 (2013)
 

 

Ripple modulated electronic structure of a 3D topological insulator

Y. Okada, W. Zhou, D. Walkup, C. Dhital, S. D. Wilson, V. Madhavan

 Nature Communications 3, 1158 (6 pages) (2012)
 

 

Visualizing Landau levels of Dirac electrons in a one dimensional potential

Y. Okada, Wenwen Zhou, Chetan. Dhital, D. Walkup, Ying Ran, Z. Wang, Stephen D. Wilson, V. Madhavan

 Phys. Rev. Lett. 109, 166407 (2012)

 

Direct Observation of Broken Time-Reversal Symmetry on the Surface of a Magnetically Doped Topological Insulator

Y. Okada, C. Dhital, W. Zhou, E. D. Huemiller, H. Lin, S. Basak, A. Bansil, Y. -B. Huang, H. Ding, Z. Wang, S. D. Wilson, and V. Madhavan

Phys. Rev. Lett. 106, 206805-206808 (2011)

 

Three energy- and temperature-scales corresponding to competing pseudogap state, incoherent-, and coherent-superconductivity in high-Tc cuprates

Y. Okada, T. Kawaguchi, M. Ohkawa, K. Ishizaka, T. Takeuchi, S. Shin, and H. Ikuta

Phys. Rev. B 83, 104502-104507 (2011).

 

Enhancement of superconducting fluctuation under the coexistence of a competing pseudogap state in Bi2Sr2-xRxCuOy

Y. Okada, Y. Kuzuya, T. Kawaguchi, and H. Ikuta

Phys. Rev. B 81, 214520-214524 (2010).

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Origin of the anomalously strong influence of out-of-plane disorder on high-Tc superconductivity

Y. Okada, T. Takeuchi, T. Baba, S. Shin, and H. Ikuta

Journal of Phys. Soc. Japan 77, 074714-074717 (2008).