Faculty Profiles - SETTAI Rikio

Papers - SETTAI Rikio

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Hall effect in the quasi two-dimensional strongly correlated metal CeMIn5 (M = Co, Rh) Reviewed

Y. Nakajima, H. Shishido, H. Nakai, T. Shibauchi, K. Izawa, K. Behnia, H. Hedo, Y. Uwatoko, T. Matsumoto, R. Settai, Y. Onuki, H. Kontani, Y. Matsuda

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 310 ( 2 ) 334 - 336 2007.3

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

We report on the evolution of the Hall effect in heavy fermion compounds CeMIn5 (M = Co, Rh), ranging from antiferromagnetic metal to Fermi liquid regime through non-Fermi liquid regime by applying pressure. We found that anomalous transport properties of CeMIn5 are strikingly similar to that of high-T-c cuprates. We also found that the magnitude of Hall coeffi. cient appears to diverge near an antiferromagnetic quantum critical point. These results strongly suggest that unusual transport properties of CeMIn5 are dominated by anisotropic scattering due to strong spin. uctuations. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2006.10.028

Anomalous quasiparticle transport and superclean superconducting state of CeCoIn5 Reviewed

Y. Kasahara, Y. Nakajima, K. Izawa, Y. Matsuda, K. Behnia, H. Shishido, R. Settai, Y. Onuki

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 310 ( 2 ) 569 - 571 2007.3

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

To investigate the quasiparticle dynamics in the superconducting state of quasi-two dimensional heavy fermion superconductor CeCoIn5, thermal conductivity tensor is measured. We obtained the quasiparticle mean free path and the density of states separately by using the combination of longitudinal thermal conductivity and thermal Hall angle. The quasiparticle mean free path increases dramatically below T-c in zero magnetic field. The density of states and the scaling relation of thermal Hall conductivity are consistent with d-wave symmetry. We also argue that CeCoIn5 is in the superclean regime. These results highlight the anomalous superconducting state in CeCoIn5 with striking similarities with high-T-c cuprates. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2006.10.154

Magnetic-field modulation of the Josephson effect in heavy-fermion superconductor CeIrIn5 Reviewed

A. Sumiyama, Y. Tsuji, Y. Oda, H. Shishido, R. Settai, Y. Onuki

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 310 ( 2 ) 599 - 601 2007.3

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

The Josephson effect between a single-crystal CeIrIn5 and an s-wave superconductor has been investigated for current. ows parallel to the [1 0 0] and [1 1 0] axes of CeIrIn5. The magnetic-field modulation of the Josephson critical current has shown a nearly ideal Fraunhofer pattern in the [1 0 0] direction and a small deviation from that pattern in the [1 1 0] direction. The clear anisotropy, which has been reported for YBa2Cu3O7-delta indicating the d- wave superconductivity, was not observed in this study. (c) 2006 Elsevier B. V. All rights reserved.

DOI： 10.1016/j.jmmm.2006.10.245

Pressure effect of electrical resistivity and AC specific heat in CePtAl Reviewed

M. Nakashima, T. Ueda, K. Shimizu, H. Nakashima, A. Thamizhavel, N. Tateiwa, Y. Haga, M. Hedo, Y. Uwatoko, R. Settai, Y. Onuki, K. Izawa, G. Knebel, B. Salce, J. Flouquet

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 310 ( 2 ) E9 - E11 2007.3

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

We measured the electrical resistivity and AC-specific heat for a canted ferromagnet CePtAl under pressures using a diamond-anvil pressure cell. With increasing pressure, the magnetic ordering temperature T-C1 increases monotonously, becomes constant above 8GPa and then starts to decrease steeply in a narrow pressure region from 10.3 to 10: 9 GPa, indicating the first-order like phase transition. The similar pressure dependence of T-C1 was obtained in the AC-specific heat measurement. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2006.10.056

Synthesis, crystal structure and magnetic properties of Yb8Ag18.5Al47.5, Yb2Pd2Cd and Yb-1.35Pd2Cd0.65 Reviewed

S. K. Dhar, R. Settai, Y. Onuki, A. Galatanu, Y. Haga, P. Manfrinetti, M. Pani

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 308 ( 1 ) 143 - 152 2007.1

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

We report the synthesis of three new Yb-based compounds, Yb8Ag18.5Al47.5 (Yb8Cu17Al49-type, tetragonal tI74-14/mmm), Yb2Pd2Cd (Mo2B2Fe-type, tetragonat tP10-P4/mbm) and Yb1.35Pd2Cd0.65 (MnCu2Al-type, cubic cF16-Fm (K) over barm). The crystal symmetry of these compounds has been determined and the complete structural characterisation carried out by single crystal and powder diffraction techniques. Two symmetry in-equivalent sites are available for the Yb ions in Yb8Ag18.5Al47.5 and Yb1.35Pd2Cd0.65. The 4f levels of the Yb ions are appreciably hybridised in Yb8Ag18.5Al47.5 and to a lesser extent in Yb2Pd2Cd as inferred from the magnetisation and heat capacity data. Signatures of heavy fermion behaviour are observed in the heat capacity data of Yb2Pd2Cd in which the heat capacity, C/T, increases at low temperatures attaining a value of approximate to 600 mJ/mol K-2 at 1.8 K. The electrical resistivity of Yb2Pd2Cd follows a linear variation with temperature, T, between 1.4 and 5 K, thus indicating a possible non-Fermi liquid behaviour. In contrast, Yb ions are trivalent in Yb1.35Pd2Cd0.65 and order magnetically near 1.4 K. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2006.05.013

Pressure-induced superconductivity in CeNiGe<inf>3</inf>

H. Kotegawa, T. Miyoshi, K. Takeda, S. Fukushima, H. Hidaka, K. Tabata, T. C. Kobayashi, M. Nakashima, A. Thamizhavel, R. Settai, Y. Onuki

Physica B: Condensed Matter 378-380 ( SPEC. ISS. ) 419 - 420 2006.5

Publishing type：Research paper (scientific journal)

An antiferromagnet CeNiGe3, which exhibits a quantum critical point at PC ∼ 6 - 7 GPa, shows the superconductivity in wide pressure range of 1.7 - 9.3 GPa. In addition to the superconductivity around PC, the sharp superconducting transition can be observed by both the resistivity and the susceptibility measurements at lower pressure region far apart from PC, where 4f-localized picture seems to be still dominant. Such a superconductivity is a first example in the f-electron systems. © 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2006.01.147

Evolution of Hall coefficient in two-dimensional heavy fermion CeCoIn5 Reviewed

Y Nakajima, K Izawa, Y Matsuda, K Behnia, H Kontani, M Hedo, Y Uwatoko, T Matsumoto, H Shishido, R Settai, Y Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 75 ( 2 ) 2006.2

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

We report on the pressure dependence of the Hall coefficient RH in quasi-2D heavy fermion CeCoIn5. At ambient pressure, below a temperature associated with the emergence of non-Fermi liquid properties, RH is anomalously enhanced. We found that the restoration of the Fermi liquid state with applied pressure leads to a gradual suppression of this dramatic enhancement. Moreover, the enhancement in RH was found to be confined to an intermediate temperature window, where inelastic electron-electron scattering is dominant. Our results strongly support the presence of cold and hot spots on the Fermi surface probably due to anisotropic scattering by antiferromagnetic fluctuations, which may also prove relevant for the debate on the anomalous normal-state properties of high-T-c cuprates.

DOI： 10.1143/JPSJ.75.023705

Change of the electronic states in CeIn3, CeRhIn5 and CePt3Si tuned by pressure Reviewed

Y Onuki, R Settai, H Shishido, Kubo, I, Y Yasuda, K Betsuyaku, H Harima

JOURNAL OF ALLOYS AND COMPOUNDS 408 27 - 32 2006.2

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

We have studied a change of the electronic states in antiferromagnets CeIn3, CeRhIn5 and CePt3Si via the de Haas-van Alphen experiments. The critical pressure P-c, where the Neel temperature becomes zero, is P-c similar or equal to 2.5 GPa in CeIn3 with the cubic crystal structure, in which the narrow pressure region superconductivity appears below a superconducting transition temperature T-sc = 0.2 K. In the pressure region P > P-c, we detected a main Fermi surface with the cyclotron mass m*(c) = 53m(0), which most likely corresponds to a nearly spherical Fermi surface in the paramagnetic state, namely a 4f-itinerant Fermi surface. The Fermi surface in the antiferromagnet CeRhIn5 with the tetragonal crystal structure is similar to that of LaRhIn5, consisting of two kinds of nearly cylindrical Fermi surfaces. We observed a drastic change of the Fermi surface from 4f-localized (LaRhIn5) to 4f-itinerant (CeCoIn5) Fermi surfaces at P-c similar or equal to 2.4 GPa. The cyclotron mass increases intensively above 1.6 GPa where superconductivity sets in. CePt3 Si with the tetragonal crystal structure without inversion symmetry is highly different from CeIn3 and CeRhIn5 in magnetism and superconductivity. It orders antiferromagnetically below T-N = 2.3 K and becomes superconductive below T-sc = 0.6 K at ambient pressure. With increasing pressure, the cyclotron mass is found to be reduced, together with a steep decrease of T-N and Tsc, where P-c is most likely about 1.5 GPa in CePt3Si. The heavy fermion state Of CePt3Si is realized at ambient pressure. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2005.04.101

Evidence for novel pairing state in noncentrosymmetric superconductor CePt3Si: Si-29-NMR knight shift study Reviewed

M Yogi, H Mukuda, Y Kitaoka, S Hashimoto, T Yasuda, R Settai, TD Matsuda, Y Haga, Y Onuki, P Rogl, E Bauer

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 75 ( 1 ) 2006.1

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

We report the measurements of the Si-29 Knight shift K-29 on the noncentrosymmetric heavy-fermion compound CePt3Si in which antiferromagnetism (AFM) with T-N = 2.2 K coexists with superconductivity (SC) with T-c = 0.75 K. Its spin part K-29(s), which is deduced to be K-s(c) >= 0.11 and 0.16% at respective magnetic fields H = 2.0061 and 0.8671 T, does not decrease across the superconducting transition temperature Tc for the field along the c-axis. The temperature dependence of nuclear spin-lattice relaxation of Pt-195 below T-c has been accounted for by a Cooper pairing model with a two-component order parameter composed of spin-singlet and spin-triplet pairing components. From this result, it is shown that the Knight-shift data are consistent with the occurrence of the two-component order parameter for CePt3Si.

DOI： 10.1143/JPSJ.75.013709

In-115-NQR study of antiferromagnetism and superconductivity in CeRhIn5 and CeIn3 under pressure Reviewed

S Kawasaki, M Yashima, H Kotegawa, T Mito, Y Kawasaki, GQ Zheng, Y Kitaoka, H Shishido, S Araki, D Aoki, Y Haga, R Settai, Y Onuki

JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 67 ( 1-3 ) 497 - 499 2006.1

Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

We report the novel phase diagram of superconductivity (SC) and anti ferromagnetism (AFM) in heavy-fermion (HF) pressure(P)-induced superconductors CeRhIn5 and CeIn5 through nuclear-quadrupole-resonance (NQR) measurements under P. The P-induced superconductivity in CeRhIn5 coexists with AFM on a microscopic level in P = 1.5-1.9 GPa. By contrast, in CeIn3, the P-induced phase separation of AFM and paramagnetism (PM) takes place without any trace of a quantum phase transition. The outstanding finding is that SC sets in at both the phases magnetically separated into AFM and PM in P=2.28-2.5 GPa. (c) 2005 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jpcs.2005.10.043

Pt-195 NMR study on noncentrosymmetric heavy-fermion superconductor CePt3Si Reviewed

M Yogi, Y Kitaoka, S Hashimoto, T Yasuda, R Settai, TD Matsuda, Y Haga, Y Onuki, P Rogl, E Bauer

JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 67 ( 1-3 ) 522 - 524 2006.1

Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

We report on magnetic and novel superconducting properties in heavy-fermion (HF) noncentrosymmetric compound CePt3Si via the measurement of Pt-195 nuclear spin-lattice relaxation rate 1/T-1. This compound reveals the uniform coexistence of antiferromagnetism (T-N = 2.2 K) and superconductivity (T-c =0.75 K). CePt3Si is the first HF superconductor that reveals a peak in 1/T-1 just below T-c and, additionally, does not follow the T-3 law that was observed for most unconventional HF superconductors. The novel relaxation behavior found below T-c may be relevant with a possible novel SC state being realized in the noncentrosymmetric CePt3Si. (c) 2005 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jpcs.2005.10.070

de Haas-van Alphen effect and the metamagnetic transition based on the quadrupole moment in PrCu <sub>2</sub>

M. Abliz, R. Settai, P. Ahmet, D. Aoki, K. Sugiyama, Y. Ōnuki

Philosophical Magazine B 2006

Anomalous quasiparticle transport in the superconducting state of CeCoIn5 Reviewed

Y. Kasahara, Y. Nakajima, K. Izawa, Y. Matsuda, K. Behnia, H. Shishido, R. Settai, Y. Onuki

Physical Review B - Condensed Matter and Materials Physics 72 ( 21 ) 2005.12

Language：English Publishing type：Research paper (scientific journal)

We report on a study of thermal Hall conductivity κxy in the superconducting state of CeCoIn5. The scaling relation and the density of states of the delocalized quasiparticles, both obtained from κxy, are consistent with d-wave superconducting symmetry. The onset of superconductivity is accompanied by a steep increase in the thermal Hall angle, pointing to a striking enhancement in the quasiparticle mean free path. This enhancement is drastically suppressed in a very weak magnetic field. These results highlight that CeCoIn5 is unique among superconductors. A small Fermi energy, a large superconducting gap, a short coherence length, and a long mean free path all indicate that CeCoIn5 is clearly in the superclean regime (εF Δ ξ), in which a peculiar vortex state is expected. © 2005 The American Physical Society.

DOI： 10.1103/PhysRevB.72.214515

Anomalous quasiparticle transport in the superconducting state of CeCoIn5 Reviewed

Y Kasahara, Y Nakajima, K Izawa, Y Matsuda, K Behnia, H Shishido, R Settai, Y Onuki

PHYSICAL REVIEW B 72 ( 21 ) 2005.12

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER PHYSICAL SOC

We report on a study of thermal Hall conductivity kappa(xy) in the superconducting state of CeCoIn5. The scaling relation and the density of states of the delocalized quasiparticles, both obtained from kappa(xy), are consistent with d-wave superconducting symmetry. The onset of superconductivity is accompanied by a steep increase in the thermal Hall angle, pointing to a striking enhancement in the quasiparticle mean free path. This enhancement is drastically suppressed in a very weak magnetic field. These results highlight that CeCoIn5 is unique among superconductors. A small Fermi energy, a large superconducting gap, a short coherence length, and a long mean free path all indicate that CeCoIn5 is clearly in the superclean regime (epsilon(F)/Delta <center dot/xi), in which a peculiar vortex state is expected.

DOI： 10.1103/PhysRevB.72.214515

Single crystal growth and Fermi surface properties of ThIn3 Reviewed

TD Matsuda, Y Haga, S Ikeda, H Shishido, R Settai, H Harima, Y Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 74 ( 12 ) 3276 - 3282 2005.12

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

We have succeeded in growing a high-quality single crystal of ThIn3 with the cubic structure by the Influx method and measured the electrical resistivity, magnetic susceptibility and de Haas-van Alphen (dHvA) effect. Several dHvA branches were observed, ranging from 5.2 x 10(6) to 1.7 x 10(8) Oe. The Fermi surface consists of a nearly spherical Fermi surface and a multiply-connected Fermi surface. The corresponding cyclotron effective masses are small, ranging from 0.31 to 1.4 m(0). These Fermi surface properties are well explained by the energy band calculations based on the FLAPW method.

DOI： 10.1143/JPSJ.74.3276

Effect of pressure on electronic states in canted ferromagnet CePtAl Reviewed

T Ueda, M Nakashima, M Hedo, Y Uwatoko, H Nakashima, A Thamizhavel, TD Matsuda, Y Haga, R Settai, Y Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 74 ( 12 ) 3393 - 3394 2005.12

Change of the Fermi surface across the critical pressure in CeIn3: The de Haas-van Alphen study under pressure Reviewed

R Settai, T Kubo, T Shiromoto, D Honda, H Shishido, K Sugiyama, Y Haga, TD Matsuda, K Betsuyaku, H Harima, TC Kobayashi, Y Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 74 ( 11 ) 3016 - 3026 2005.11

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

We have studied a change of the Fermi surface in an antiferromagnet CeIn3 via the de Haas-van Alphen experiment under pressure up to 3 GPa. With increasing pressure P, the Neel temperature T-N = 10 K decreases and becomes zero at a critical pressure P-c similar or equal to 2.6 GPa. In the pressure region P > P,, we have observed a large main Fermi surface named a, which indicates that the electronic state of 4f electron in CeIn3 changes from localized to itinerant at P-c, as observed in the similar antiferromagnets CeRh2Si2 and CeRhIn5. The cyclotron effective mass m(c)(*) of this main Fermi surface is extremely enhanced around P-c: m(c)(*) similar or equal to 60m(0) at 2.7 GPa for the magnetic field along the (100) direction.

DOI： 10.1143/JPSJ.74.3016

Josephson effect between CePt3Si and an s-wave superconductor Reviewed

A Sumiyama, K Nakatsuji, Y Tsuji, Y Oda, T Yasuda, R Settai, Y Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 74 ( 11 ) 3041 - 3045 2005.11

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

Josephson critical current I-c between a single crystal CePt3Si and Al has been measured for the junctions on the CePt3Si surface perpendicular to the a and c axes. In the magnetic-field dependence of I-c a dominant maximum peak at zero field has been observed only for the junction on the a-axis face thus far, indicating that the Josephson effect is allowed at least for current flow parallel to the a axis. This result places a restriction on the representations of the order parameter in the noncentrosymmetric superconductor CePt3Si.

DOI： 10.1143/JPSJ.74.3041

New high field state of flux line lattice in CeCoIn5 Reviewed

Y Kasahara, T Watanabe, K Izawa, T Sakakibara, CJ van der Beek, T Hanaguri, M Nohara, H Takagi, H Shishido, R Settai, Y Onuki, Y Matsuda

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 426 36 - 40 2005.10

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

We have measured the ultrasound velocity of quasi-two-dimensional superconductor CeCoIn5 with extremely large Pauli paramagnetic susceptibility. The results indicate that the new high field superconducting phase, which is revealed by the recent heat capacity measurements, is characterized by the unusual softening of flux line lattice. The softening is most likely due to the collapse of the flux line lattice tilt modulus and transition to quasi-two-dimensional vortex state. These results provide a strong evidence that the high field phase is the Fulde-Ferrell-Larkin-Ovchinnikov phase, in which the order parameter is spatially modulated and has planar nodes aligned perpendicularly to the vortices. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2005.02.018

Multiple superconducting phases in heavy fermion superconductors Reviewed

Y Matsuda, K Izawa, T Watanabe, Y Kasahara, Y Nakajima, T Sakakibara, CJ van der Beek, M Nohara, T Hanaguri, H Takagi, J Goryo, K Maki, P Thalmeier, S Osaki, H Sugawara, H Sato, H Shishido, R Settai, Y Onuki

JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 66 ( 8-9 ) 1365 - 1369 2005.8

Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

We show that in recently discovered heavy fermion superconductors, quasi two-dimensional CeCoIn5 and skutterudite PrOs4Sb12, multiple superconducting phases with different symmetries manifest themselves below T-c. The ultrasound velocity measurements revealed that in CeCoIn5 the Fulde-Ferrel-Larkin-Ovchinikov phase, in which the order parameter is spatially modulated and has planar nodes aligned perpendicular to the vortices, appears at low temperature and high field. The angle resolved magnetothermal transport measurements revealed that in PrOs4Sb12 a novel change in the symmetry of the superconducting gap function occurs deep inside the superconducting state. These results open up a new realm for the study of the superconductivity with multiple phases. (c) 2005 Published by Elsevier Ltd.

DOI： 10.1016/j.jpcs.2005.05.012

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