Coexisting spin resonance and long-range magnetic order of Eu in EuRbFeAs

Iida, Kazuki*; Nagai, Yuki; Ishida, Shigeyuki*; Ishikado, Motoyuki*; Murai, Naoki; Christianson, A. D.*; Yoshida, Hiroyuki*; Inamura, Yasuhiro; Nakamura, Hiroki; Nakao, Akiko*; et al.

Physical Review B, 100(1), p.014506_1 - 014506_8, 2019/07

https://doi.org/10.1103/PhysRevB.100.014506

Magnetic excitations and magnetic structure of EuRbFeAs were investigated by neutron scattering measurements.

Spontaneous decays of magneto-elastic excitations in non-collinear antiferromagnet (Y,Lu)MnO

Oh, J.*; Le, M. D.*; Nahm, H.-H.*; Sim, H.*; Jeong, J.*; Perring, T. G.*; Woo, H.*; Nakajima, Kenji; Kawamura, Seiko; Yamani, Z.*; et al.

Nature Communications (Internet), 7, p.13146_1 - 13146_6, 2016/10

https://doi.org/10.1038/ncomms13146

Magnons and phonons are fundamental quasiparticles in a solid and can be coupled together to form a hybrid quasi-particle. However, detailed experimental studies on the underlying Hamiltonian of this particle are rare for actual materials. Moreover, the anharmonicity of such magnetoelastic excitations remains largely unexplored, although it is essential for a proper understanding of their diverse thermodynamic behaviour and intrinsic zero-temperature decay. Here we show that in non-collinear antiferromagnets, a strong magnon phonon coupling can significantly enhance the anharmonicity, resulting in the creation of magnetoelastic excitations and their spontaneous decay. By measuring the spin waves over the full Brillouin zone and carrying out anharmonic spin wave calculations using a Hamiltonian with an explicit magnon phonon coupling, we have identified a hybrid magnetoelastic mode in (Y,Lu)MnO and quantified its decay rate and the exchange-striction coupling termrequired to produce it.

Inelastic neutron scattering on iron-based superconductor BaFe(As,P)

Ishikado, Motoyuki; Kodama, Katsuaki; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Wakimoto, Shuichi; Iyo, Akira*; Eisaki, Hiroshi*; Arai, Masatoshi; Shamoto, Shinichi

Physica C, 471(21-22), p.643 - 646, 2011/11

https://doi.org/10.1016/j.physc.2011.05.016

Superconducting gap symmetry of 1111 system, which has the highest in iron-based superconductors, is considered to be full gap wave based on magnetic penetration depth and neutron scattering measurements. On the other hand, a line node gap symmetry is proposed in BaFe(As,P) based on magnetic penetration depth and thermal conductivity measurements despite comparatively its high- (=30 K). Inelastic neutron scattering of BaFe(As,P) may exhibit different magnetic excitations in the -position or -dependence of a resonant peak from that of La1111 system. In this study, we performed inelastic neutron scattering measurement on 36g polycrystalline powder sample of optimally-doped BaFe(As,P) using Fermi chopper spectrometer 4SEASONS in J-PARC. We will discuss about the possible superconducting gap symmetry based on our inelastic neutron scattering results.

-like spin resonance in the iron-based nodal superconductor BaFe(AsP) 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

We performed inelastic neutron scattering on a powder sample of iron-based superconductor BaFe(AsP) with = 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 -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 and KFeAs ( 10 K).

Angle-resolved photoemission spectroscopy study of PrFeAsO; Comparison with LaFePO

Nishi, Ichiro*; Ishikado, Motoyuki; Ideta, Shinichiro*; Malaeb, W.*; Yoshida, Teppei*; Fujimori, Atsushi*; Kotani, Yoshinori*; Kubota, Masato*; Ono, Kanta*; Yi, M.*; et al.

Physical Review B, 84(1), p.014504_1 - 014504_5, 2011/07

https://doi.org/10.1103/PhysRevB.84.014504

We have performed an angle-resolved photoemission spectroscopy (ARPES) study of the iron-based superconductor PrFeAsO and examined the Fermi surfaces and band dispersions near the fermi level. Heavily hole-doped electronic states have been observed due to the polar nature of the cleaved surfaces. Nevertheless, we have found that the ARPES spectra basically agree with band dispersions calculated in the local density approximation (LDA) if the bandwidth is reduced by a factor of 2.5 and then the chemical potential is lowered by 70 meV. Comparison with previous ARPES results on LaFePO reveals that the energy positions of the - and -derived bands are considerably different between the two materials, which we attribute to the different pnictogen height as predicted by the LDA calculation.

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

https://doi.org/10.1126/science.1198415

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 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 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 (), entangled in an energy-momentum dependent manner with the preexisting pseudogap features, ushering in a ground state with coexisting orders.

Spin excitations in iron oxypnictide superconductor system

Shamoto, Shinichi; Ishikado, Motoyuki; Wakimoto, Shuichi; Kodama, Katsuaki; Kajimoto, Ryoichi; Arai, Masatoshi; Fukuda, Tatsuo; Nakamura, Hiroki; Machida, Masahiko; Eisaki, Hiroshi*

Physica C, 470(Suppl.1), p.S284 - S287, 2010/12

https://doi.org/10.1016/j.physc.2009.11.132

Lower critical fields and the anisotropy in PrFeAsO single crystals

Okazaki, Ryuji*; Konczykowski, M.*; Van der Beek, C. J.*; Kato, Tomonari*; Hashimoto, Kenichiro*; Shimozawa, Masaaki*; Shishido, Hiroaki*; Yamashita, Minoru*; Ishikado, Motoyuki; Kito, Hijiri*; et al.

Physica C, 470(Suppl.1), p.S485 - S486, 2010/12

https://doi.org/10.1016/j.physc.2009.12.041

We report the lower critical fields measurements on Fe-based oxipnictide PrFeAsO single crystals for and -planes. To avoid the difficulty of determinations due to the flux pinning, we developed a novel method using a miniature hall-sensor array which can evaluate the local magnetic induction ai each sensor position. The hall sensor which is placed on the edge of the crystal clearly resolves the first flux penetration from the Meissner state. The temperature dependence of for is well scaled by the in-plane penetration depth and is consistent with a full-gap superconducting state. The anistropy of at low temperatures is estimated to be 3, which is much smaller than of . This indicates the multiband superconductivity, in which the active bands for superconductivity are more two-dimensional.

Interlayer Josephson couplings in Hg-based multi-layered cuprates

Hirata, Yasuyuki*; Kojima, Kenji*; Uchida, Shinichi*; Ishikado, Motoyuki; Iyo, Akira*; Eisaki, Hiroshi*; Tajima, Setsuko*

Physica C, 470(Suppl.1), p.S44 - S46, 2010/12

https://doi.org/10.1016/j.physc.2009.10.120

Infrared reflectivity spectra of the multilayered HgBaCaCuO ( = 2, 3, 4, and 5) are measured. Optical plasma modes associated with the Josephson coupling between CuO planes within a multilayer appear below in the c-axis component of the reflectivity spectrum. For the bilayer and trilayer compound an optical Josephson plasma mode appears at unprecedentedly high frequency, 700-800 cm, below . The plasma frequencies appreciably decrease in four- and five-layer compounds which indicates the suppression of superconducting order in the inner CuO planes, consistent with the result of NMR experiment.

Degradation of superconductivity and spin fluctuations by electron overdoping in LaFeAsOF

Wakimoto, Shuichi; Kodama, Katsuaki; Ishikado, Motoyuki; Matsuda, Masaaki; Kajimoto, Ryoichi; Arai, Masatoshi; Kakurai, Kazuhisa; Esaka, Fumitaka; Iyo, Akira*; Kito, Hijiri*; et al.

Journal of the Physical Society of Japan, 79(7), p.074715_1 - 074715_4, 2010/07

https://doi.org/10.1143/JPSJ.79.074715