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Journal Articles

Horizontal line nodes in Sr$$_2$$RuO$$_4$$ proved by spin resonance

Iida, Kazuki*; Kofu, Maiko; Suzuki, Katsuhiro*; Murai, Naoki; Kawamura, Seiko; Kajimoto, Ryoichi; Inamura, Yasuhiro; Ishikado, Motoyuki*; Hasegawa, Shunsuke*; Masuda, Takatsugu*; et al.

Journal of the Physical Society of Japan, 89(5), p.053702_1 - 053702_5, 2020/05

https://doi.org/10.7566/JPSJ.89.053702
 Times Cited Count：19 Percentile：81.08(Physics, 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

https://doi.org/10.1103/PhysRevB.97.241112
 Times Cited Count：5 Percentile：25.82(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

Switching of intra-orbital spin excitations in electron-doped iron pnictide superconductors

Iimura, Soshi*; Matsuishi, Satoru*; Miyakawa, Masashi*; Taniguchi, Takashi*; Suzuki, Katsuhiro*; Usui, Hidetomo*; Kuroki, Kazuhiko*; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; et al.

Physical Review B, 88(6), p.060501_1 - 060501_5, 2013/08

https://doi.org/10.1103/PhysRevB.88.060501
 Times Cited Count：26 Percentile：71.33(Materials Science, Multidisciplinary)

Journal Articles

Theoretical analysis for inelastic neutron scattering on BaFe$$_{2}$$(As$$_{1-x}$$,P$$_{x}$$)$$_{2}$$ using realistic three-dimensional 10-orbital tight-binding model

Nagai, Yuki; Nakamura, Hiroki; Suzuki, Katsuhiro*; Usui, Hidetomo*; Kuroki, Kazuhiko*; Machida, Masahiko

Journal of the Physical Society of Japan, 80(Suppl.B), p.SB021_1 - SB021_4, 2011/12

https://doi.org/10.1143/JPSJS.80SB.SB021
 Times Cited Count：0 Percentile：0(Physics, Multidisciplinary)

We calculate spin susceptibility on the basis of the multi-orbital random-phase approximation with use of the realistic three-dimensional 10-orbital tight-binding model for an iron-based superconductor BaFe$$_{2}$$(As$$_{1-x}$$,P$$_{x}$$)$$_{2}$$ which seems to have gap-nodes. We show that the shape of nodes on the Fermi surface for BaFe$$_{2}$$(As$$_{1-x}$$,P$$_{x}$$)$$_{2}$$ is distinguishable according to inelastic neutron scattering experiments. Our results are consistent with the recent neutron scattering experiments for BaFe$$_{2}$$(As$$_{1-x}$$,P$$_{x}$$)$$_{2}$$ with Tc = 30 K.

Journal Articles

$$s_{pm}$$-like spin resonance in the iron-based nodal superconductor BaFe$$_2$$(As$$_{0.65}$$P$$_{0.35}$$)$$_2$$ observed using inelastic neutron scattering

Ishikado, Motoyuki; Nagai, Yuki; Kodama, Katsuaki; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Wakimoto, Shuichi; Nakamura, Hiroki; Machida, Masahiko; Suzuki, Katsuhiro*; et al.

Physical Review B, 84(14), p.144517_1 - 144517_5, 2011/10

https://doi.org/10.1103/PhysRevB.84.144517
 Times Cited Count：26 Percentile：70.69(Materials Science, Multidisciplinary)

We performed inelastic neutron scattering on a powder sample of iron-based superconductor BaFe$$_2$$(As$$_{0.65}$$P$$_{0.35}$$)$$_2$$ with $$T_c$$ = 30 K. Although this system is expected to have line nodes in its superconducting order parameter, we have observed spin resonance at the same scattering vector as that appeared in the $$s_{pm}$$-wave iron-based superconductors without line nodes. Moreover, the resonance enhancement, which can be a measure of the area of sign reversal between the hole and electron Fermi surfaces (FSs), is comparable to those without line nodes. These facts indicate that the sign reversal between the FSs is still dominant in this system, and the line nodes should create only limited area of sign-reversal on a single FS. Hence the system can hold higher Tc than the other iron-based superconductors with nodal symmetry, such as LaFePO$$_{1-y}$$ and KFe$$_2$$As$$_2$$ ($$T_c <$$ 10 K).

Oral presentation

Polarized neutron diffractometry of Fe$${}_{16}$$N$${}_{2}$$ nanoparticles

Tamai, Yuta; Ishii, Yuya*; Hagiya, Hiroyuki; Kikuchi, Takayuki*; Yokoyama, Makoto*; Nishihara, Yoshikazu*; Takeda, Masayasu; Kakurai, Kazuhisa; Oku, Takayuki; Shinohara, Takenao; et al.

no journal, , 

Magnetic recording tape is widely used for a massive data storage with high reliability, and further increase of capacity, the recording density, is requested by IT organizations. The needle-shaped ferromagnetic metals has been used for the recording media. However, it is necessary to make the media a small and spherical shape to increase the recording density. We have performed the polarized neutron diffraction measurements of Fe$$_{16}$$N$$_{2}$$ round-shape nanoparticles, and determined the saturation magnetic moments and averaged core size of Fe$$_{16}$$N$$_{2}$$ nanoparticles covered by a laminate layer.

Oral presentation

A Polarized SANS study of spherical Fe-N nanoperticles for magnetic recording tape, 3

Hagiya, Hiroyuki; Oku, Takayuki; Kira, Hiroshi; Shinohara, Takenao; Suzuki, Junichi; Takeda, Masayasu; Tamai, Yuta; Kakurai, Kazuhisa; Sasaki, Yuji*; Kishimoto, Mikio*; et al.

no journal, , 

no abstracts in English

Oral presentation

Inelastic neutron scattering on iron-based superconductors

Ishikado, Motoyuki; Nagai, Yuki; Kodama, Katsuaki; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Mizuno, Fumio; Wakimoto, Shuichi; Nakamura, Hiroki; Machida, Masahiko; et al.

no journal, , 

Three years have passed since the discovery of iron-based superconductors, its maximum superconducting transition temperature ($$T_c$$) is 55 K, resulting in second highest material system next to cuprate high-$$T_c$$ superconductors. Among various material systems in iron-based superconductors, we have systematically studied on LaFeAsO$$_{1-x}$$F$$_x$$ ($$T_c^{max}$$=28 K) of first discovered system and BaFe$$_2$$(As,P)$$_2$$ which have recently attracted tremendous attention by the discovery of line nodes in its order parameter. In the session, we present recent results on "spin fluctuation and superconductivity on LaFePO$$_{0.9}$$", and "symmetry of order parameter on BaFe$$_2$$(As,P)$$_2$$ by inelastic neutron scattering" studied by the chopper spectrometer 4SEASONS (J-PARC).

Oral presentation

Resonant spin excitation on iron-based superconductor BaFe$$_2$$(As,P)$$_2$$

Ishikado, Motoyuki; Nagai, Yuki; Kodama, Katsuaki; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Wakimoto, Shuichi; Nakamura, Hiroki; Machida, Masahiko; Suzuki, Katsuhiro*; et al.

no journal, , 

In this study, we have performed inelastic neutron scattering measurement on 36g powder sample of optimally-doped BaFe$$_2$$(As,P)$$_2$$ whose superconducting order parameter is expected to have line node by Fermi chopper spectrometer 4SEASONS in J-PARC. Unexpectedly, we have observed spin resonance at same $$Q$$-position and nearly identical resonance enhancement ration to other iron-based superconducctors with fully-gapped $$s_{+-}$$-wave. We will discuss about the possible superconducting gap symmetry based on our experimental results.

Oral presentation

Inelastic neutron scattering studies on iron-based high-$$T_c$$ superconductors

Ishikado, Motoyuki; Kodama, Katsuaki; Wakimoto, Shuichi; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Mizuno, Fumio; Nagai, Yuki; Nakamura, Hiroki; Machida, Masahiko; et al.

no journal, , 

Among various iron-based superconductors, we have systematically studied on LaFeAsO$$_{1-x}$$F$$_x$$ ($$T_c^{max}$$=28 K) and BaFe$$_2$$(As,P)$$_2$$ ($$T_c^{max}$$=31 K) by the Fermi chopper spectrometer 4SEASONS (J-PARC). We will discuss the possible relation between high-$$T_c$$ superconductivity and magnetic fluctuation based on our inelastic neutron scattering results.

Oral presentation

Spin resonance on Fe-based superconductor BaFe$$_2$$(As,P)$$_2$$ with nodal gap symmetry

Ishikado, Motoyuki; Kodama, Katsuaki; Wakimoto, Shuichi; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Nagai, Yuki; Nakamura, Hiroki; Machida, Masahiko; Suzuki, Katsuhiro*; et al.

no journal, , 

In this study, we performed inelastic neutron scattering measurement on 36g polycrystalline powder sample of optimally-doped BaFe$$_2$$(As$$_{0.65}$$P$$_{0.35}$$)$$_2$$ using a Fermi chopper spectrometer 4SEASONS in J-PARC. We observed strong spin resonance at the same $$Q$$-position similar to those of other iron-based superconductors with fully-gapped $$s_{pm}$$-wave. We will discuss about the possible superconducting gap symmetry and what causes relatively high-$$T_{rm c}$$ of this material based on our inelastic neutron scattering results.

Oral presentation

Magnetic scattering on Fe-based superconductors La1111 and BaFe$$_2$$(As,P)$$_2$$

Ishikado, Motoyuki; Nagai, Yuki; Kodama, Katsuaki; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Mizuno, Fumio; Wakimoto, Shuichi; Nakamura, Hiroki; Machida, Masahiko; et al.

no journal, , 

We report systematic studies on Fe-based superconductors LaFeAsO$$_{1-x}$$F$$_x$$ ($$T^{max}_{rm c}$$ =28 K) and BaFe$$_2$$(As,P)$$_2$$ ($$T^{max}_{rm c}$$ =31 K) by using inelastic neutron scattering measurement.

Oral presentation

Spin resonance mode on Fe-based superconductor BaFe$$_2$$(As,P)$$_2$$ with $$T_{rm c}$$=30K

Ishikado, Motoyuki; Nagai, Yuki; Kodama, Katsuaki; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Wakimoto, Shuichi; Nakamura, Hiroki; Machida, Masahiko; Suzuki, Katsuhiro*; et al.

no journal, , 

In this study, we performed inelastic neutron scattering measurement on 36g polycrystalline powder sample of optimally-doped BaFe$$_2$$(As$$_{0.65}$$,P$$_{0.35}$$)$$_2$$ using Fermi chopper spectrometer 4SEASONS in J-PARC. Unexpectedly, we observed spin resonance at the same $$Q$$-position and nearly identical resonance enhancement ratio to other iron-based superconductors with fully-gapped $$s_{pm}$$-wave. We will discuss about the possible superconducting gap symmetry based on our inelastic neutron scattering experiment and theoretical calculations.

Oral presentation

Spin resonance on nodal iron-based high-TC superconductors

Ishikado, Motoyuki; Kodama, Katsuaki; Wakimoto, Shuichi; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Mizuno, Fumio; Nagai, Yuki; Nakamura, Hiroki; Machida, Masahiko; et al.

no journal, , 

We have systematically studied nodal iron-based superconductor LaFePO$$_{0.9}$$ ($$T_{rm c}$$=5 K) and BaFe$$_2$$(As,P)$$_2$$ ($$T_{rm c}$$=30 K) by using Fermi chopper spectrometer 4SEASONS (J-PARC) and Triple Axis Spectrometer (TAS-1) at JRR-3. In the session, we will discuss the relation between superconductivity and spin fluctuation.

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.

Oral presentation

Three-dimensional electronic structure and multiple superconducting gaps of Ba$$_{0.75}$$K$$_{0.25}$$Fe$$_{2}$$As$$_{2}$$ as seen via time-of-flight neutron spectroscopy

Kajimoto, Ryoichi; Kofu, Maiko; Kawamura, Seiko; Suzuki, Katsuhiro*; Nakajima, Masamichi*; Murai, Naoki

no journal, , 

The spin dynamics of iron-based superconductors is believed to play an essential role in the pairing mechanism, but realistic modeling of magnetic neutron scattering spectra in these materials remains challenging owing to their complex multi-band structure. Here we report the results of inelastic neutron scattering measurements of Ba$$_{0.75}$$K$$_{0.25}$$Fe$$_{2}$$As$$_{2}$$ that provide a benchmark of an ab-initio approach of the dynamical spin susceptibility. Our main results are two-fold. First, the magnetic neutron scattering response exhibits periodic intensity modulation along the out-of-plane direction. The observed periodicity corresponds to the out-of-plane warping of Fermi surfaces, revealing the importance of nesting in three-dimensional momentum space. Second, our careful measurements reveal the existence of the theoretically predicted multiple resonant modes that result from the multiple superconducting gaps. The agreement between theory and experiment in the present work highlights the potential of neutron spectroscopy to investigate the complex multi-band structure of iron-based superconductors.

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