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Journal Articles

Hybridization of Bogoliubov quasiparticles between adjacent CuO$$_2$$ layers in the triple-layer cuprate Bi$$_2$$Sr$$_2$$Ca$$_2$$Cu$$_3$$O$$_{10+delta}$$ studied by angle-resolved photoemission spectroscopy

Ideta, Shinichiro*; Johnston, S.*; Yoshida, Teppei*; Tanaka, Kiyohisa*; Mori, Michiyasu; Anzai, Hiroaki*; Ino, Akihiro*; Arita, Masashi*; Namatame, Hirofumi*; Taniguchi, Masaki*; et al.

Physical Review Letters, 127(21), p.217004_1 - 217004_6, 2021/11

Journal Articles

Absence of ferromagnetism in MnBi$$_2$$Te$$_4$$/Bi$$_2$$Te$$_3$$ down to 6 K

Fukasawa, Takuro*; Kusaka, Shotaro*; Sumida, Kazuki; Hashizume, Mizuki*; Ichinokura, Satoru*; Takeda, Yukiharu; Ideta, Shinichiro*; Tanaka, Kiyohisa*; Shimizu, Ryota*; Hitosugi, Taro*; et al.

Physical Review B, 103(20), p.205405_1 - 205405_6, 2021/05

 Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)

Journal Articles

Fabrication of a novel magnetic topological heterostructure and temperature evolution of its massive Dirac cone

Hirahara, Toru*; Otrokov, M. M.*; Sasaki, Taisuke*; Sumida, Kazuki*; Tomohiro, Yuta*; Kusaka, Shotaro*; Okuyama, Yuma*; Ichinokura, Satoru*; Kobayashi, Masaki*; Takeda, Yukiharu; et al.

Nature Communications (Internet), 11, p.4821_1 - 4821_8, 2020/09

 Times Cited Count:11 Percentile:89.19(Multidisciplinary Sciences)

Journal Articles

Devil's staircase transition of the electronic structures in CeSb

Kuroda, Kenta*; Arai, Yosuke*; Rezaei, N.*; Kunisada, So*; Sakuragi, Shunsuke*; Alaei, M.*; Kinoshita, Yuto*; Bareille, C.*; Noguchi, Ryo*; Nakayama, Mitsuhiro*; et al.

Nature Communications (Internet), 11, p.2888_1 - 2888_9, 2020/06

 Times Cited Count:3 Percentile:42.38(Multidisciplinary Sciences)

Journal Articles

Experimental investigation of the suppressed superconducting gap and double-resonance mode in Ba$$_{1-x}$$K$$_{x}$$Fe$$_{2}$$As$$_{2}$$

Ideta, Shinichiro*; Murai, Naoki; Nakajima, Masamichi*; Kajimoto, Ryoichi; Tanaka, Kiyohisa*

Physical Review B, 100(23), p.235135_1 - 235135_7, 2019/12

 Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)

Journal Articles

Effect of electron correlations on spin excitation bandwidth in Ba$$_{0.75}$$K$$_{0.25}$$Fe$$_{2}$$As$$_{2}$$ as seen via time-of-flight inelastic neutron scattering

Murai, Naoki; Suzuki, Katsuhiro*; Ideta, Shinichiro*; Nakajima, Masamichi*; Tanaka, Kiyohisa*; Ikeda, Hiroaki*; Kajimoto, Ryoichi

Physical Review B, 97(24), p.241112_1 - 241112_6, 2018/06

 Times Cited Count:5 Percentile:39.54(Materials Science, Multidisciplinary)

We use inelastic neutron scattering (INS) to investigate the effect of electron correlations on spin dynamics in iron-based superconductor Ba$$_{0.75}$$K$$_{0.25}$$Fe$$_{2}$$As$$_{2}$$. Our INS data show a spin-wave-like dispersive feature, with a zone boundary energy of 200 meV. A first principles analysis of dynamical spin susceptibility, incorporating the mass renormalization factor of 3, as determined by angle-resolved photoemission spectroscopy, provides a reasonable description of the observed spin excitations. This analysis shows that electron correlations in the Fe-3d bands yield enhanced effective electron masses, and consequently, induce substantial narrowing of the spin excitation bandwidth. Our results highlight the importance of electron correlations in an itinerant description of the spin excitations in iron-based superconductors.

Journal Articles

From a single-band metal to a high-temperature superconductor via two thermal phase transitions

He, R.-H.*; Hashimoto, Makoto*; Karapetyan, H.*; Koralek, J. D.*; Hinton, J. P.*; Testaud, J. P.*; Nathan, V.*; Yoshida, Yoshiyuki*; Yao, H.*; Tanaka, Kiyohisa*; et al.

Science, 331(6024), p.1579 - 1583, 2011/03

 Times Cited Count:252 Percentile:98.82(Multidisciplinary Sciences)

The nature of the pseudogap phase of cuprate high-temperature superconductors is a major unsolved problem in condensed matter physics. We studied the commencement of the pseudogap state at temperature $$T^*$$ using three different techniques (angle-resolved photoemission spectroscopy, polar Kerr effect, and time-resolved reflectivity) on the same optimally doped Bi2201 crystals. We observed the coincident, abrupt onset at $$T^*$$ of a particle-hole asymmetric antinodal gap in the electronic spectrum, a Kerr rotation in the reflected light polarization, and a change in the ultrafast relaxational dynamics, consistent with a phase transition. Upon further cooling, spectroscopic signatures of superconductivity begin to grow close to the superconducting transition temperature ($$T_c$$), entangled in an energy-momentum dependent manner with the preexisting pseudogap features, ushering in a ground state with coexisting orders.

Journal Articles

Crossover from coherent quasiparticles to incoherent hole carriers in underdoped cuprates

Hashimoto, Makoto*; Yoshida, Teppei*; Tanaka, Kiyohisa*; Fujimori, Atsushi*; Okusawa, Makoto*; Wakimoto, Shuichi; Yamada, Kazuyoshi*; Kakeshita, Teruhisa*; Eisaki, Hiroshi*; Uchida, Shinichi*

Physical Review B, 79(14), p.140502_1 - 140502_4, 2009/04

 Times Cited Count:13 Percentile:52.72(Materials Science, Multidisciplinary)

Journal Articles

Relationship between the superconducting gap and the pseudogap; Temperature-dependent photoemission study of La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$ and La$$_{2}$$CuO$$_{4.10}$$

Hashimoto, Makoto*; Tanaka, Kiyohisa*; Yoshida, Teppei*; Fujimori, Atsushi*; Okusawa, Makoto*; Wakimoto, Shuichi; Yamada, Kazuyoshi*; Kakeshita, Teruhisa*; Eisaki, Hiroshi*; Uchida, Shinichi*

Physica C, 460-462(2), p.884 - 885, 2007/09

 Times Cited Count:3 Percentile:18.97(Physics, Applied)

In the high-${it T$_{rm c}$}$ research, relationship between the pseudogap and the superconducting gap has been an important issue. We have performed a detailed temperature-dependent angle-integrated photoemission study of lightly-doped to heavily-overdoped La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$ and oxygen-doped La$$_{2}$$CuO$$_{4.10}$$. We found that, while the magnitude of the pseudogap increased with decreasing doping, that of the superconducting gap did not increase. This behavior can be explained if the superconducting gap opens only on the Fermi arc around the node (0,0)-($$pi$$,$$pi$$) whereas the pseudogap opens primarily around ($$pi$$,0).

Journal Articles

Distinct doping dependences of the pseudogap and superconducting gap of La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$ cuprate superconductors

Hashimoto, Makoto*; Yoshida, Teppei*; Tanaka, Kiyohisa*; Fujimori, Atsushi*; Okusawa, Makoto*; Wakimoto, Shuichi; Yamada, Kazuyoshi*; Kakeshita, Teruhisa*; Eisaki, Hiroshi*; Uchida, Shinichi*

Physical Review B, 75(14), p.140503_1 - 140503_4, 2007/04

 Times Cited Count:64 Percentile:89.48(Materials Science, Multidisciplinary)

We have performed a temperature-dependent angle-integrated photoemission study of La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$ covering from lightly doped to heavily overdoped regions and oxygen -doped La$$_{2}$$CuO$$_{4.10}$$. The superconducting gap energy $$Delta_{sc}$$ was found to remain small for decreasing hole concentration while the pseudogap energy $$Delta^{*}$$ and temperature $$T^{*}$$ increase. The different behaviors of the superconducting gap and the pseudogap can be explained if the superconducting gap opens only on the Fermi arc around the nodal (0,0)-$$(pi,pi)$$ direction while the pseudogap opens around $$sim (pi,0)$$. The results suggest that the pseudogap and the superconducting gap have different microscopic origins.

Oral presentation

ARPES study on heavy fermion superconductor CeIrSi$$_3$$ without inversion symmetry

Fujimori, Shinichi; Mo, S.-K.*; Tanaka, Kiyohisa*; Hussain, Z.*; Shen, Z. X.*; Fujimori, Atsushi; Yamagami, Hiroshi; Settai, Rikio*; Onuki, Yoshichika*

no journal, , 

We have performed angle resolved photoelectron spectroscopy study on CeIrSi$$_3$$, which does not have inversion symmetry in its crystal structure. The experiments were done in Advanced Light Source BL10.0.1. We have found that 4f derived bands mix with the ligand d bands. This result suggests that 4f electrons in this compound have some itinerant character.

Oral presentation

Two distinct resonance-like excitations in underdoped Ba_${1-x}$K_${x}$Fe_${2}$As_${2}$ (x = 0.25) as seen via inelastic neutron scattering

Murai, Naoki; Kajimoto, Ryoichi; Ikeuchi, Kazuhiko*; Tanaka, Kiyohisa*; Nakajima, Masamichi*; Ideta, Shinichiro*; Suzuki, Katsuhiro*

no journal, , 

We report an inelastic neutron scattering (INS) study of underdoped Ba_${1-x}$K_${x}$Fe_${2}$As_${2}$ that shows the presence of double-resonance at the same commensurate wave vector in the superconducting (SC) state. By comparing our INS data with the SC gap structure of the same crystal, as measured by angle-resolved photoemission spectroscopy (ARPES), we show that the observed double-resonance feature originates neither from SC gap anisotropy nor from multiple SC gaps on different Fermi-surface sheets. This suggests that the double-resonance feature in iron-pnictides cannot be interpreted within a spin-exciton scenario.

Oral presentation

Large downward renormalization of spin excitation energies in Ba$$_{0.75}$$K$$_{0.25}$$Fe$$_{2}$$As$$_{2}$$ due to electron correlation effects

Murai, Naoki; Kajimoto, Ryoichi; Suzuki, Katsuhiro*; Ideta, Shinichiro*; Nakajima, Masamichi*; Ikeda, Hiroaki*; Tanaka, Kiyohisa*

no journal, , 

Using inelastic neutron scattering (INS) and angle-resolved photoemission spectroscopy (ARPES), we investigate the spin dynamics of iron-based superconductor Ba$$_{0.75}$$K$$_{0.25}$$Fe$$_{2}$$As$$_{2}$$. The INS data show a spin-wave-like dispersive feature, with a zone boundary energy of 200 meV. A random phase approximation (RPA) treatment of the dynamical spin susceptibility, incorporating the band renormalization factor of 3 derived from the ARPES measurements on the same crystals, provides a reasonable description of the observed spin excitations. This analysis shows that the experimental spin excitation peak lies at a much lower energy than the bare value, reflecting a strong renormalization of the quasiparticle band dispersion near the Fermi level due to electron correlation effect. The present results point to a unified framework that connects the magnetic response to the underlying electronic structure of the materials.

Oral presentation

Large downward renormalization of spin excitation energies in Ba$$_{1-x}$$K$$_{x}$$Fe$$_{2}$$As$$_{2}$$ due to electron correlation effects

Murai, Naoki; Kajimoto, Ryoichi; Suzuki, Katsuhiro*; Ikeda, Hiroaki*; Nakajima, Masamichi*; Ideta, Shinichiro*; Tanaka, Kiyohisa*

no journal, , 

no abstracts in English

Oral presentation

Large downward renormalization of spin excitation energies in Ba$$_{0.75}$$K$$_{0.25}$$Fe$$_{2}$$As$$_{2}$$ due to electron correlation effects

Murai, Naoki; Kajimoto, Ryoichi; Suzuki, Katsuhiro*; Nakajima, Masamichi*; Ikeda, Hiroaki*; Ideta, Shinichiro*; Tanaka, Kiyohisa*

no journal, , 

We report inelastic neutron scattering (INS) study of hole-doped iron-based superconductor Ba$$_{1-x}$$K$$_{x}$$Fe$$_{2}$$As$$_{2}$$ (x = 0.25). The INS data show a spin-wave-like dispersive feature, with a zone boundary energy of 200 meV. A random phase approximation (RPA) treatment of the dynamical spin susceptibility, incorporating the band renormalization factor of 3 derived from angle-resolved photoemission spectroscopy (ARPES) measurements on the same sample, provides a reasonable description of the observed spin excitations. This analysis shows that the Fe-3d bandwidth narrowing due to electron correlation is directly reflected in the spin excitation energy scale. We will discuss the current state of our analysis relating the magnetic response to the underlying electronic structure of the materials.

Oral presentation

Effect of electron correlations on spin excitation bandwidth in Ba$$_{0.75}$$K$$_{0.25}$$Fe$$_{2}$$As$$_{2}$$ as seen via time-of-flight inelastic neutron scattering

Murai, Naoki; Kajimoto, Ryoichi; Suzuki, Katsuhiro*; Ikeda, Hiroaki*; Nakajima, Masamichi*; Ideta, Shinichiro*; Tanaka, Kiyohisa*

no journal, , 

We use inelastic neutron scattering (INS) to investigate the effect of electron correlations on spin dynamics in iron-based superconductor Ba$$_{0.75}$$K$$_{0.25}$$Fe$$_{2}$$As$$_{2}$$. Our INS data show a spin-wave-like dispersive feature, with a zone boundary energy of 200 meV. A first principles analysis of dynamical spin susceptibility, incorporating the mass renormalization factor of 3, as determined by angle-resolved photoemission spectroscopy, provides a reasonable description of the observed spin excitations. This analysis shows that electron correlations in the Fe-3d bands yield enhanced effective electron masses, and consequently, induce substantial narrowing of the spin excitation bandwidth. Our results highlight the importance of electron correlations in an itinerant description of the spin excitations in iron-based superconductors.

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