Faculty Profiles - SETTAI Rikio

Papers - SETTAI Rikio

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Novel pressure phase diagram of heavy fermion superconductor CePt3Si investigated by ac calorimetry Reviewed

N Tateiwa, Y Haga, TD Matsuda, S Ikeda, T Yasuda, T Takeuchi, R Settai, Y Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 74 ( 7 ) 1903 - 1906 2005.7

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

The pressure dependences of the antiferromagnetic and superconducting transition temperatures have been investigated by ac heat capacity measurement under high pressures for the heavy-fermion superconductor CePt3Si without inversion symmetry in the tetragonal structure. The Neel temperature T-N = 2.2 K decreases with increasing pressure and becomes zero at the critical pressure P-AF similar or equal to 0.6 GPa. On the other hand, the superconducting phase exists in a wider pressure region from ambient pressure to about 1.5 GPa. The pressure phase diagram of CePt3Si is thus very unique and has never been reported before for other heavy fermion superconductors.

DOI： 10.1143/JPSJ.74.1903

Bulk-sensitive photoemission spectroscopy of Pr-based filled skutterudites Reviewed

A Yamasaki, S Imada, A Sekiyama, M Tsunekawa, T Nanba, C Dallera, L Braicovich, TL Lee, H Sugawara, H Sato, C Sekine, Shirotani, I, R Settai, Y Onuki, H Harima, S Suga

JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA 144 621 - 623 2005.6

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

Bulk electronic structures of Pr-based filled skutterudites and their reference materials have been investigated by bulk-sensitive photoemission spectroscopy using soft and hard X-rays. For Pr 3d-4f resonance, a strong intensity in the vicinity of Fermi level (EF) is observed only for PrFe4P12. Furthermore, PrFC4P12 has the significant spectral weight of the vertical bar 3d(9)4f(3)> final state in Pr 3d core-level spectrum. We interpret that the observed prominent intensity just below EF arises from a Kondo resonance due to the strong hybridization between the Pr 4f and conduction states. (c) 2005 Elsevier B.V. All Rights Reserved.

DOI： 10.1016/j.elspec.2005.01.025

Line nodes in the superconducting gap function of noncentrosymmetric CePt3Si Reviewed

K Izawa, Y Kasahara, Y Matsuda, K Behnia, T Yasuda, R Settai, Y Onuki

PHYSICAL REVIEW LETTERS 94 ( 19 ) 2005.5

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

The superconducting gap structure of recently discovered heavy fermion CePt3Si without spatial inversion symmetry was investigated by thermal transport measurements down to 40 mK. In zero field a residual T-linear term was clearly resolved as T -> 0, with a magnitude in good agreement with the value expected for a residual normal fluid with a nodal gap structure, together with a T-2 dependence at high temperatures. With an applied magnetic field, the thermal conductivity grows rapidly, in dramatic contrast to fully gapped superconductors, and exhibits one-parameter scaling with T/root(H) over bar. These results place an important constraint on the order parameter symmetry; that is, CePt3Si is most likely to have line nodes.

DOI： 10.1103/PhysRevLett.94.197002

Pressure dependence of the first-order superconducting phase transition in CeCoIn5 Reviewed

T Tayama, Y Namai, T Sakakibara, M Hedo, Y Uwatoko, H Shishido, R Settai, Y Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 74 ( 4 ) 1115 - 1118 2005.4

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

The pressure dependence of the first-order phase transition (FOPT) at the upper critical field H-c2 in CeCoIn5 has been Studied by magnetization measurements. The FOPT is found to persist at pressures at least up to 1.5 GPa in the c axis and up to 1.38 GPa in the a axis. With increasing pressure, the anisotropy of H-c2 becomes stronger, and the condensation energy decreases significantly. We also observed a notable peak effect near H-c2 under pressure. Our results suggest that the FOPT cannot be accounted for by Pauli limiting alone.

DOI： 10.1143/JPSJ.74.1115

Ordered magnetic and quadrupolar states under hydrostatic pressure in orthorhombic PrCu2 Reviewed

T Naka, LA Ponomarenko, A de Visser, A Matsushita, R Settai, Y Onuki

PHYSICAL REVIEW B 71 ( 2 ) 2005.1

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

We report magnetic susceptibility and electrical resistivity measurements under hydrostatic pressure up to 2 GPa on single-crystalline PrCu2, which exhibits the pressure-induced Van Vleck paramagnet-to-antiferromagnet transition at 1.2 GPa. The measured anisotropy in the susceptibility shows that the ordered 4f moments lie in the ac plane in the pressure-induced magnetic state. We propose that remarkable pressure effects on the susceptibility and resistivity are due to changes in the quadrupolar state of O-2(2) and/or O-2(0) under pressure. We present a simple analysis in terms of the singlet-singlet model.

DOI： 10.1103/PhysRevB.71.024408

Fermi surface of LaRu4 P12: A clue to the origin of the metal-insulator transition in PrRu4 P12 Reviewed

S. R. Saha, H. Sugawara, Y. Aoki, H. Sato, Y. Inada, H. Shishido, R. Settai, Y. Onuki, H. Harima

Physical Review B - Condensed Matter and Materials Physics 71 ( 13 ) 2005

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

We report the de Haas-van Alphen (dHvA) effect and magnetoresistance in the filled-skutterudite superconductor LaRu4 P12, which is a reference material of PrRu4 P12 that exhibits a metal-insulator (M-I) transition at TMI 60 K. The observed dHvA branches for the main Fermi surface (FS) are well explained by the band-structure calculation, using the full potential linearized augmented-plane-wave method with the local-density approximation, suggesting a nesting instability with q= (1,0,0) in the main multiply connected FS as expected also in PrRu4 P12. Observed cyclotron effective masses of (2.6-11.8) m0, which are roughly twice the calculated masses, indicate the large mass enhancement even in the La-skutterudites. Comparing the FS between LaRu4 P12 and PrRu4 P12, an essential role of c-f hybridization cooperating with the FS nesting in driving the M-I transition in PrRu4 P12 is clarified. © 2005 The American Physical Society.

DOI： 10.1103/PhysRevB.71.132502

Evidence for direct CP violation in B-0 -> K+pi(-) decays Reviewed

Y Chao, P Chang, K Abe, K Abe, N Abe, Adachi, I, H Aihara, K Akai, M Akatsu, M Akemoto, Y Asano, T Aso, Aulchenko, V, T Aushev, T Aziz, S Bahinipati, AM Bakich, Y Ban, M Barbero, A Bay, Bedny, I, U Bitenc, Bizjak, I, S Blyth, A Bondar, A Bozek, M Bracko, J Brodzicka, TE Browder, MC Chang, A Chen, KF Chen, WT Chen, BG Cheon, R Chistov, SK Choi, Y Choi, YK Choi, A Chuvikov, S Cole, M Danilov, M Dash, LY Dong, R Dowd, J Dragic, A Drutskoy, S Eidelman, Eiges, V, Y Enari, D Epifanov, CW Everton, F Fang, J Flanagan, S Fratina, H Fujii, Y Funakoshi, K Furukawa, N Gabyshev, A Garmash, T Gershon, A Go, G Gokhroo, B Golob, MG Perdekamp, H Guler, R Guo, J Haba, C Hagner, F Handa, K Hara, T Hara, NC Hastings, K Hasuko, K Hayasaka, H Hayashii, M Hazumi, EM Heenan, Higuchi, I, T Higuchi, L Hinz, T Hojo, T Hokuue, Y Hoshi, K Hoshina, S Hou, WS Hou, YB Hsiung, HC Huang, T Igaki, Y Igarashi, T Iijima, H Ikeda, A Imoto, K Inami, A Ishikawa, H Ishino, K Itoh, R Itoh, M Iwamoto, M Iwasaki, Y Iwasaki, R Kagan, H Kakuno, T Kamitani, JH Kang, JS Kang, P Kapusta, SU Kataoka, N Katayama, H Kawai, H Kawai, Y Kawakami, N Kawamura, T Kawasaki, N Kent, HR Khan, A Kibayashi, H Kichimi, M Kikuchi, E Kikutani, HJ Kim, HO Kim, H Kim, JH Kim, SK Kim, TH Kim, K Kinoshita, S Kobayashi, H Koiso, P Koppenburg, S Korpar, P Krizan, P Krokovny, T Kubo, R Kulasiri, S Kumar, CC Kuo, H Kurashiro, E Kurihara, A Kusaka, A Kuzmin, YJ Kwon, JS Lange, G Leder, SE Lee, SH Lee, YJ Lee, T Lesiak, J Li, A Limosani, SW Lin, D Liventsev, J MacNaughton, G Majumder, F Mandl, D Marlow, M Masuzawa, T Matsuishi, H Matsumoto, S Matsumoto, T Matsumoto, A Matyja, S Michizono, Y Mikami, T Mimashi, W Mitaroff, K Miyabayashi, Y Miyabayashi, H Miyake, H Miyata, R Mizuk, D Mohapatra, GR Moloney, GF Moorhead, T Mori, J Mueller, A Murakami, T Nagamine, Y Nagasaka, T Nakadaira, Nakamura, I, TT Nakamura, E Nakano, M Nakao, H Nakayama, H Nakazawa, Z Natkaniec, K Neichi, S Nishida, O Nitoh, S Noguchi, T Nozaki, A Ogawa, S Ogawa, Y Ogawa, K Ohmi, Y Ohnishi, T Ohshima, N Ohuchi, K Oide, T Okabe, S Okuno, SL Olsen, Y Onuki, W Ostrowicz, H Ozaki, P Pakhlov, H Palka, CW Park, H Park, KS Park, N Parslow, LS Peak, M Pernicka, JP Perroud, M Peters, LE Piilonen, A Poluektov, FJ Ronga, N Root, M Rozanska, H Sagawa, M Saigo, S Saitoh, Y Sakai, H Sakamoto, H Sakaue, TR Sarangi, M Satapathy, N Sato, T Schietinger, O Schneider, J Schumann, C Schwanda, AJ Schwartz, T Seki, S Semenov, K Senyo, Y Settai, R Seuster, ME Sevior, T Shibata, H Shibuya, T Shidara, B Shwartz, Sidorov, V, Siegle, V, JB Singh, A Somov, N Soni, R Stamen, S Stanic, M Staric, R Sugahara, A Sugi, T Sugimura, A Sugiyama, K Sumisawa, T Sumiyoshi, S Suzuki, SY Suzuki, SK Swain, O Tajima, F Takasaki, K Tamai, N Tamura, K Tanabe, M Tanaka, M Tawada, GN Taylor, Y Teramoto, XC Tian, S Tokuda, SN Tovey, K Trabelsi, T Tsuboyama, T Tsukamoto, K Uchida, S Uehara, T Uglov, K Ueno, Y Unno, S Uno, Y Ushiroda, G Varner, KE Varvell, S Villa, CC Wang, CH Wang, JG Wang, MZ Wang, M Watanabe, Y Watanabe, L Widhalm, QL Xie, BD Yabsley, A Yamaguchi, H Yamamoto, N Yamamoto, S Yamamoto, T Yamanaka, Y Yamashita, M Yamauchi, H Yang, P Yeh, J Ying, K Yoshida, M Yoshida, Y Yuan, Y Yusa, H Yuta, SL Zang, CC Zhang, J Zhang, LM Zhang, ZP Zhang, Y Zheng, Zhilich, V, T Ziegler, D Zontar, D Zurcher

PHYSICAL REVIEW LETTERS 93 ( 19 ) 2004.11

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

We report evidence for direct CP violation in the decay B-0-->K(+)pi(-) with 253 fb(-1) of data collected with the Belle detector at the KEKB e(+)e(-) collider. Using 275x10(6) B(B) over bar pairs we observe a B-->K(+/-)pi(-/+) signal with 2140+/-53 events. The measured CP violating asymmetry is A(CP)(K(+)pi(-))=-0.101+/-0.025(stat)+/-0.005(syst), corresponding to a significance of 3.9sigma including systematics. We also search for CP violation in the decays B+-->K(+)pi(0) and B+-->pi(+)pi(0). The measured CP violating asymmetries are A(CP)(K(+)pi(0))=0.04+/-0.05(stat)+/-0.02(syst) and A(CP)(pi(+)pi(0))=-0.02+/-0.10(stat)+/-0.01(syst), corresponding to the intervals -0.05< A(CP)(K(+)pi(0))<0.13 and -0.18< A(CP)(pi(+)pi(0))<0.14 at 90% confidence level.

DOI： 10.1103/PhysRevLett.93.191802

Pressure-induced superconductivity in UIr Reviewed

T Akazawa, H Hidaka, H Kotegawa, TC Kobayashi, T Fujiwara, E Yamamoto, Y Haga, R Settai, Y Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73 ( 11 ) 3129 - 3134 2004.11

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

Pressure-induced superconductivity is found in UIr without inversion symmetry. The pressure-temperature phase diagram has been investigated by means of the electrical resistivity and magnetization measurements under high pressure. The phase diagram consists of two magnetic phases, the Ising-like ferromagnetic phase (FM1) at low pressures and another magnetic phase (FM2) with the small ferromagnetic component along the [101] direction at high pressures. Superconductivity is observed in the narrow pressure range near the disappearance point of the FM2 phase, where the temperature dependence of resistivity follows the non-Fermi liquid form of T-1.6. From these experimental facts, the superconductivity is considered to be associated with the critical fluctuation with the disappearance of FM2 phase.

DOI： 10.1143/JPSJ.73.3129

Two kinds of cylindrical fermi surface determined by de Haas-van alphen experiments in NpCoGa5 Reviewed

D Aoki, Y Homma, Y Shiokawa, E Yamamoto, A Nakamura, Y Haga, R Settai, Y Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73 ( 10 ) 2608 - 2611 2004.10

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

We succeeded in observing de Haas-van Alphen (dHvA) oscillations in an antiferromagnet NpCoGa5 with a tetragonal structure. The dHvA signal was significantly enhanced at higher fields than the metamagnetic transition field H-m (= 43 kOe for H parallel to [001]), where the antiferromagnetic state is changed into the field-induced ferromagnetic (paramagnetic) state. In the paramagnetic state, the Fermi surface was found to consist of two kinds of cylindrical main Fermi surface and small pocket Fermi surfaces. The cyclotron masses of the main Fermi surfaces were considerably large, ranging from 6 to 12 m(0). This is the first case where the Fermi surface was determined experimentally in transuranium compounds.

DOI： 10.1143/JPSJ.73.20608

Two Kinds of Cylindrical Fermi Surfce Determined by de Haas-van Alphen Experiments in NpCoGa5 Reviewed

D. Aoki, Y. Homma, Y.Shiokawa, E. Yamamoto, A. Nakamura, Y. Haga, R. Settai, T. Takeuchi, Y. Onuki

J. Phys. Soc. Japan 73 ( 10 ) 1 - 4 2004.10

High-resolution angle-resolved photoemission study of LaRh3B2 Reviewed

Y Iida, S Souma, T Sato, T Takahashi, M Yamada, T Okubo, T Shiromoto, Y Inada, R Settai, Y Onuki

PHYSICA B-CONDENSED MATTER 351 ( 3-4 ) 271 - 273 2004.9

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

We report high-resolution angle-resolved photoemission spectroscopy of LaRh3B2, which is a nonmagnetic reference compound of RRh3B2 (R: rare-earth metals). We found two hole-like Fermi surfaces (FSs) and two electron-like FSs centered at Gamma(A) and K(H) points, respectively. The estimated volume of FSs at Gamma(A) point shows a good agreement with the LDA band calculation, while the band dispersion and the topology of FSs at K(H) point show a remarkable disagreement. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2004.06.023

Small saturation moment due to the crystalline electric field effect for T-h site symmetry in the ferromagnet UFe4P12 Reviewed

TD Matsuda, A Galatanu, Y Haga, S Ikeda, E Yamamoto, M Hedo, Y Uwatoko, T Takeuchi, K Sugiyama, K Kindo, R Settai, Y Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73 ( 9 ) 2533 - 2538 2004.9

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

Electrical resistivity, specific heat, magnetic susceptibility and high-field magnetization measurements have been performed on the ferromagnet UFe4P12 with the cubic crystal structure. The ferromagnetic ordering at T-C = 3.1 K, a small saturation moment of 1.3 mu(B)/U, together with the temperature dependence of the magnetic susceptibility, are found to be well explained by considering the 5f(2) crystalline electric field schemes for T-h site symmetry and the magnetic exchange interaction.

DOI： 10.1143/JPSJ.73.2533

Magnetic and fermi surface properties of an antiferromagnet Ce3Sn7 Reviewed

Y Okuda, T Takeuchi, T Yamamoto, D Honda, H Shishido, A Galatanu, TD Matsuda, Y Haga, K Kindo, K Sugiyama, R Settai, Y Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73 ( 8 ) 2276 - 2282 2004.8

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

We measured the electrical resistivity, specific heat, magnetic susceptibility, high-field magnetization, thermal expansion and magnetostriction of an antiferromagnet Ce3Sn7 with the orthorhombic crystal structure. The experimental data are found to be well explained on the basis of the crystalline electric field (CEF) 4f-scheme previously proposed by Bonnet et al. in which the two Cc atoms at the 2(a) site possess a magnetic moment of 0.36 /mu(B)/Ce and the one Ce atom at the 4(i) site possesses no magnetic moment as in a valence fluctuating compound CeSn3. We also constructed the antiferromagnetic phase diagram for the three principal directions. Furthermore, we carried out the de Haas-van Alphen experiment. Fermi surfaces are many in number but extremely small in volumes, indicating that Ce3Sn7 is a semimetal.

DOI： 10.1143/JPSJ.73.2276

Magnetic and fermi surface properties in PrRh3B2 Reviewed

M Yamada, Y Obiraki, T Okubo, T Shiromoto, Y Kida, M Shiimoto, H Kohara, T Yamamoto, D Honda, A Galatanu, Y Haga, T Takeuchi, K Sugiyama, R Settai, K Kindo, SK Dhar, H Harima, Y Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73 ( 8 ) 2266 - 2275 2004.8

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

We have grown a single crystal of PrRh3B2 with the hexagonal structure and measured the electrical resistivity, specific heat, de Haas-van Alphen oscillation, magnetic susceptibility, high-field magnetization, thermal expansion and magnetostriction. PrRh3B2 is not a simple ferromagnet as reported previously, but a ferrimagnet with an ordering temperature T-ord = 3.6 K. The Schottky specific heat observed around 25 K and the large anisotropy of the magnetic susceptibility and magnetization are found to be well explained by the crystalline electric field (CEF) with a large overall CEF-splitting energy of 1080 K and a strong ferromagnetic exchange interaction along the [0001] direction. The topology of the Fermi surface in PrRh3B2 is Similar to that of the non-4f reference compound LaRh3B2, exhibiting a quasi-one-dimensional character of the electronic states.

DOI： 10.1143/JPSJ.73.2266

High-field state of the flux-line lattice in the unconventional superconductor CeCoIn5 Reviewed

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

PHYSICAL REVIEW B 70 ( 2 ) 2004.7

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

Ultrasound velocity measurements of the unconventional superconductor CeCoIn5 with extremely large Pauli paramagnetic susceptibility reveal an unusual structural transformation of the flux-line lattice (FLL) in the vicinity of the upper critical field. The transition field coincides with that at which heat capacity measurements reveal a second-order phase transition. The lowering of the sound velocity at the transition is consistent with vortex segmentation and a crossover to quasi-two-dimensional FLL pinning. These results provide strong evidence that the high-field state is the Fulde-Ferrel-Larkin-Ovchinikov phase, in which the order parameter is spatially modulated and has planar nodes aligned perpendicular to the vortices.

DOI： 10.1103/PhysRevB.70.020506

Single crystal growth of large-size and high-quality NpCoGa5 and its electrical and magnetic properties Reviewed

D Aoki, Y Homma, Y Shiokawa, E Yamamoto, A Nakamura, Y Haga, R Settai, T Takeuchi, Y Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73 ( 7 ) 1665 - 1668 2004.7

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

We succeeded in growing a high-quality NpCoGa5 single crystal by the Ga-flux method and measured its electrical resistivity, specific heat, magnetic susceptibility and magnetization. NpCoGa5 is an antiferromagnet with a Neel temperature of 47 K. The magnetic moment of Np is directed along the [001] direction of a tetragonal crystal structure. A sharp metamagnetic transition was observed at H-m = 43 kOe for H || [001], where the antiferromagnetic state is changed to the paramagnetic state above H-m. The ordered moment was determined to be 0.74 mu(B)/Np. The magnetic properties were discussed on the basis of the crystalline electric field scheme of the 5f(4) configuration.

DOI： 10.1143/JPSJ.73.1665

Superconducting property in CePt3Si under pressure Reviewed

T Yasuda, H Shishido, T Ueda, S Hashimoto, R Settai, T Takeuchi, TD Matsuda, Y Haga, Y Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73 ( 7 ) 1657 - 1660 2004.7

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

We have studied the superconducting property by measuring the electrical resistivity under the magnetic field and pressure for CePt3Si, which is the first antiferromagnetic heavy fermion superconductor without inversion symmetry in its tetragonal crystal structure. The upper critical field H-c2(0) is found to be approximately isotropic: H-c2(0) = 2.7 T for H || [100] and 3.2 T for H || [001]. The Neel temperature T-N = 2.3 K and the zero resistivity superconducting transition temperature T-sc similar or equal to 0.65 K decrease markedly with increasing pressure, suggesting that the present superconductivity is correlated to the anti ferromagnetic state.

DOI： 10.1143/JPSJ.73.1657

Magnetism and superconductivity in a heavy-fermion superconductor, CePt3Si Reviewed

T Takeuchi, S Hashimoto, T Yasuda, H Shishido, T Ueda, M Yamada, Y Obiraki, M Shiimoto, H Kohara, T Yamamoto, K Sugiyama, K Kindo, TD Matsuda, Y Haga, Y Aoki, H Sato, R Settai, Y Onuki

JOURNAL OF PHYSICS-CONDENSED MATTER 16 ( 28 ) L333 - L342 2004.7

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

We have studied the magnetic and thermal properties of a single crystal of CePt3Si, which is a recently reported heavy-fermion superconductor with a superconducting transition temperature T-c = 0.75 K and a Neel temperature T-N = 2.2 K. The overall experimental data are principally explained on the basis of the crystalline electric field (CEF) scheme. Even in the antiferromagnetic state, the CEF model applies well to the characteristic features in the magnetization curve. These results indicate the existence of a localized magnetic moment at the Ce site, with a considerably reduced ordered moment of 0.16 mu(B)/Ce, and the strongly correlated conduction electrons are condensed into the superconducting state. We have also constructed the magnetic phase diagram including the superconducting phase for H parallel to [110] and [001].

DOI： 10.1088/0953-8984/16/28/L03

High-field state of the flux-line lattice in the unconventional superconductor CeCoIn5 Reviewed

T. Watanabe, Y. Kasahara, K. Izawa, T. Sakakibara, Y. Matsuda, C. J. Van Der Beek, T. Hanaguri, H. Shishido, R. Settai, Y. Onuki

Physical Review B - Condensed Matter and Materials Physics 70 ( 2 ) 1 - 20506 2004.7

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

Ultrasound velocity measurements of the unconventional superconductor CeCoIn5 with extremely, large Pauli paramagnetic susceptibility reveal an unusual structural transformation of the flux-line lattice (FLL) in the vicinity of the upper critical field. The transition field coincides with that at which heat capacity measurements reveal a second-order phase transition. The lowering of the sound velocity at the transition is consistent with vortex segmentation and a crossover to quasi-two-dimensional FLL pinning. These results provide strong evidence that the high-field state is the Fulde-Ferrel-Larkin- Ovchinikov phase, in which the order parameter is spatially modulated and has planar nodes aligned perpendicular to the vortices.

DOI： 10.1103/PhysRevB.70.020506

The de Haas-van Alphen effect and the Fermi surface in CePt3Si and LaPt3Si Reviewed

S Hashimoto, T Yasuda, T Kubo, H Shishido, T Ueda, R Settai, TD Matsuda, Y Haga, H Harima, Y Onuki

JOURNAL OF PHYSICS-CONDENSED MATTER 16 ( 23 ) L287 - L296 2004.6

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

We have carried out a de Hass-van Alphen (dHvA) experiment for the recently discovered CePt3Si, which is the first heavy fermion superconductor without inversion symmetry in the tetragonal crystal structure, together with a dHvA experiment for a non-4f reference compound LaPt3Si. As for LaPt3Si, several dHvA branches were observed. Among them, the two main dHvA branches with the dHvA frequency (the cyclotron effective mass) of 1.10 x 10(8) Oe (1.4 m(0)) and 8.41 x 10(7) Oe (1.5 m(0)) were found to be well explained from the FLAPW energy band calculations, corresponding to bands 64- and 63-multiply-connected hole Fermi surfaces, respectively. On the other hand, the dHvA frequencies of 10(7) Oe in CePt3Si are small in magnitude, although the corresponding cyclotron masses of 10-20 m(0) are extremely large.

DOI： 10.1088/0953-8984/16/23/L02

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