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Journal Articles

Pseudo-triplet 5$$f$$ electron state in the heavy fermion superconductor NpPd$$_5$$Al$$_2$$

Metoki, Naoto; Aoki, Dai*; Griveau, J.-C.*; Otsuki, Junya*

Journal of the Physical Society of Japan, 89(2), p.024707_1 - 024707_6, 2020/02

 Times Cited Count:2 Percentile:14.51(Physics, Multidisciplinary)

The pseudo triplet ground state in the heavy-fermion superconductor NpPd$$_5$$Al$$_2$$ was concluded. The magnetic susceptibility $$chi$$ can be reproduced by the singlet ground state $$Gamma_{t1}$$ with the main component of $$|0rangle$$ and the first excited doublet $$Gamma_{t5}$$ dominated by $$|pm1rangle$$ at $$Delta E=49$$,K. The magnetization curve can be explained from the effective local hamiltonian for pseudo spin $$J$$=1 with $$DJ_z^2$$($$D=Delta E$$) equivalent to the quadrupole operator $$O_{20}$$. The specific heat can be described with the Kondo model normalized to give the entropy R$$ln3$$, corresponding to the pseudo triplet state. The derived Kondo temperature $$T_{rm K}=55$$,K comparable to the level splitting $$Delta E=49$$,K indicates the contribution of the excited doublet $$Gamma_{t5}$$ to the possible multi-channel Kondo effect.

Journal Articles

High-field phase diagram of the heavy-fermion metal CeIn$$_3$$; Pulsed-field NMR study on single crystals up to 56 T

Tokunaga, Yo; Orlova, A.*; Bruyant, N.*; Aoki, Dai*; Mayaffre, H.*; Kr$"a$mer, S.*; Julien, M.-H.*; Berthier, C.*; Horvati$'c$, M.*; Higa, Nonoka; et al.

Physical Review B, 99(8), p.085142_1 - 085142_5, 2019/02

 Times Cited Count:1 Percentile:76.22(Materials Science, Multidisciplinary)

The heavy-fermion antiferromagnet CeIn$$_3$$ exhibits a field-induced anomaly associated with Fermi surface reconstruction at $$H^*sim$$ 45 T, well below the antiferromagnetic (AFM) critical field that exceeds 60 T. In order to explore the origin of this anomaly, we have measured $$^{115}$$In NMR spectra in pulsed magnetic fields up to 56 T using high-quality single crystals. To within experimental resolution, we do not detect any change in the NMR spectra that could suggest a modification in either the character of the hyperfine field or the electric field gradient at In sites through $$H^*$$. This strongly suggests that the 45 T anomaly cannot be simply ascribed to a field-induced change in the magnetic structure of the AFM state.

Journal Articles

Revising the 4${it f}$ symmetry in CeCu$$_{2}$$Ge$$_{2}$$; Soft X-ray absorption and hard X-ray photoemission spectroscopy

Aratani, Hidekazu*; Nakatani, Yasuhiro*; Fujiwara, Hidenori*; Kawada, Moeki*; Kanai, Yuina*; Yamagami, Kohei*; Fujioka, Shuhei*; Hamamoto, Satoru*; Kuga, Kentaro*; Kiss, Takayuki*; et al.

Physical Review B, 98(12), p.121113_1 - 121113_6, 2018/09


 Times Cited Count:3 Percentile:64.52(Materials Science, Multidisciplinary)

Journal Articles

Evidence for momentum-dependent heavy fermionic electronic structures; Soft X-ray ARPES for the superconductor CeNi$$_{2}$$Ge$$_{2}$$ in the normal state

Nakatani, Yasuhiro*; Aratani, Hidekazu*; Fujiwara, Hidenori*; Mori, Takeo*; Tsuruta, Atsushi*; Tachibana, Shoichi*; Yamaguchi, Takashi*; Kiss, Takayuki*; Yamasaki, Atsushi*; Yasui, Akira*; et al.

Physical Review B, 97(11), p.115160_1 - 115160_7, 2018/03


 Times Cited Count:1 Percentile:87.78(Materials Science, Multidisciplinary)

Journal Articles

Josephson effect and point-contact spectroscopy studies of the anomaly observed in the superconducting state of the heavy-fermion compound UBe$$_{13}$$

Gochi, Jun; Sumiyama, Akihiko*; Yamaguchi, Akira*; Motoyama, Gaku*; Haga, Yoshinori; Onuki, Yoshichika

Journal of the Physical Society of Japan, 84(9), p.094714_1 - 094714_5, 2015/09

 Times Cited Count:1 Percentile:85.31(Physics, Multidisciplinary)

Journal Articles

Colossal thermomagnetic response in the exotic superconductor URu$$_2$$Si$$_2$$

Yamashita, Takuya*; Shimoyama, Yusuke*; Haga, Yoshinori; Matsuda, Tatsuma*; Yamamoto, Etsuji; Onuki, Yoshichika; Sumiyoshi, Hiroaki*; Fujimoto, Satoshi*; Levchenko, A.*; Shibauchi, Takasada*; et al.

Nature Physics, 11(1), p.17 - 20, 2015/01

 Times Cited Count:32 Percentile:11.24(Physics, Multidisciplinary)

Journal Articles

Josephson effect between UPt$$_3$$ and conventional superconductors under pressure

Gochi, Jun*; Sumiyama, Akihiko*; Yamaguchi, Akira*; Motoyama, Gaku*; Kimura, Noriaki*; Yamamoto, Etsuji; Haga, Yoshinori; Onuki, Yoshichika

JPS Conference Proceedings (Internet), 3, p.011067_1 - 011067_6, 2014/06

Journal Articles

Magnetism and superconductivity in CePt$$_3$$Si probed by muon spin relaxation

Higemoto, Wataru; Haga, Yoshinori; Matsuda, Tatsuma; Onuki, Yoshichika; Koda, Akihiro*; Saha, S. R.*; Oishi, Kazuki; Kadono, Ryosuke*

Journal of the Physical Society of Japan, 75(Suppl.), p.180 - 182, 2006/08

We report on the Magnetism, magnetic penetration depth and the Knight shift in polycrystalline sample of CePt$$_3$$Si by means of muon spin rotation and relaxation method. The appearance of the internal field under the zero magnetic field in whole volume of the specimen, was observed, which indicating clear evidence of antiferromagnetism. The muon Knight shift was measured down to 20mK at 17kOe. Three different frequencies are seen in the muon spin rotation spectra, which depend on the temperature. The symmetry of the superconducting Cooper pair will be discussed.

Journal Articles

Thermodynamics Investigation on pressure-induced superconductor CeNiGe$$_3$$ by ac calorimetry

Tateiwa, Naoyuki; Haga, Yoshinori; Matsuda, Tatsuma; Ikeda, Shugo; Nakashima, Miho*; Thamizhavel, A.*; Settai, Rikio*; Onuki, Yoshichika

Journal of the Physical Society of Japan, 75(Suppl.), p.174 - 176, 2006/08

We have investigated the physical properties of Heavy Fermion superconductors by the ac calorimetry under high pressure using a thermocouple. The method is powerful tool since the high sensitive measurement of the heat capacity is possible and the precise pressure dependence of transition temperatures such as the superconducting transition can be determined. In this conference, I would like to report our investigations on the heavy fermion superconductors CePt$$_3$$Si, CeNiGe$$_3$$ and UIr. We have made pressure phase diagram of these compounds and discuss the relation between the magnetism and superconductivity.

Journal Articles

Direct observation of a quasiparticle band in CeIrIn$$_5$$; An Angle-resolved photoemission spectroscopy study

Fujimori, Shinichi; Fujimori, Atsushi; Shimada, Kenya*; Narimura, Takamasa*; Kobayashi, Kenichi*; Namatame, Hirofumi*; Taniguchi, Masaki*; Harima, Hisatomo*; Shishido, Hiroaki*; Ikeda, Shugo; et al.

Physical Review B, 73(22), p.224517_1 - 224517_5, 2006/06

 Times Cited Count:38 Percentile:17.43(Materials Science, Multidisciplinary)

We have performed a high-resolution angle resolved Ce 4$$d$$-4$$f$$ resonant photoemission experiment on the heavy fermion superconductor CeIrIn$$_5$$. We have observed a quasi-particle band which has a energy disepersion of $$sim$$ 30 meV in the Ce 4$$f$$ on-resonance spectra. The result suggests that although the Ce 4$$f$$ spectra are dominated by the localized/correlated character being dominant, the small itinerant component is responsible for the superconductivity in this compound.

Journal Articles

Anomalous magnetic correlations in heavy fermion Pauli paramagnet UIr$$_3$$B$$_2$$; $$^{11}$$B NMR study

Fujimoto, Tatsuya; Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Walstedt, R. E.; Ikeda, Shugo; Matsuda, Tatsuma; Haga, Yoshinori; Onuki, Yoshichika

Physica B; Condensed Matter, 378-380, p.997 - 998, 2006/05

 Times Cited Count:0 Percentile:100(Physics, Condensed Matter)

We report $$^{11}$$B NMR results of a single crystal UIr$$_3$$B$$_2$$. The measurement was performed by Fast Fourier Transformation technique, because spectral line width is extremely narrow ($$simeq$$ 10 kHz) and NMR occurs in quite limited r.f. band due to a good sample quality. From temperature variation of Knight shift and nuclear spin-lattice relaxation rate, the development of ferromagnetic correlations was clarified in the temperature range above $$T^{*} simeq 50$$ K. On the other hand, the magnetic dynamics was changed into another novel state below $$T^{*}$$; ferromagnetic correlations are restrained, meanwhile antiferromagnetic correlations are newly emerged. To explain this characteristic ground state, the one-dimensional $$5f$$ electrons state due to the unique structural lattice of UIr$$_3$$B$$_2$$ was proposed.

Journal Articles

Soft X-ray synchrotron radiation photoemission study on uranium compounds

Fujimori, Shinichi; Terai, Kota; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Muramatsu, Yasuji; Fujimori, Atsushi; Yamagami, Hiroshi*; Ikeda, Shugo; Matsuda, Tatsuma; et al.

Physica B; Condensed Matter, 378-380, p.995 - 996, 2006/05

 Times Cited Count:2 Percentile:86.32(Physics, Condensed Matter)

Recently, photoemission experiments in soft X-ray region have attracted much attention due to their high sensitivities for bulk electronic structures of strongly correlated electron system. We have carried out the high-resolution photoemission experiments on some uranium compounds using soft X-ray synchrotron radiation from SPring-8 to understand their electronic structures. Bulk- and U 5$$f$$-sensitive band structure and Fermi surface were obtained for itinerant U 5$$f$$ compounds UFeGa$$_5$$ and USb$$_2$$, and they are compared with the results of the band structure calculations treating U 5$$f$$ states as being itinerant. In addition, we show the results of photoemission study on some heavy fermion compounds such as UPd$$_2$$Al$$_3$$ and UNi$$_2$$Al$$_3$$. The temperature dependences of the U 5$$f$$ electronic structure of UPd$$_2$$Al$$_3$$ will be also reported.

Journal Articles

Magnetic structure and crystal field excitation in heavy fermion superconductor CePt$$_{3}$$Si

Metoki, Naoto; Kaneko, Koji; Matsuda, Tatsuma; Galatanu, A.; Takeuchi, Tetsuya*; Hashimoto, Shin*; Ueda, Taiki*; Settai, Rikio*; Onuki, Yoshichika*; Bernhoeft, N.*

Physica B; Condensed Matter, 359-361, p.383 - 385, 2005/06

 Times Cited Count:1 Percentile:93.23(Physics, Condensed Matter)

no abstracts in English

Journal Articles

Magnetic structure and the crystal field excitation in heavy-fermion antiferromagnetic superconductor CePt$$_{3}$$Si

Metoki, Naoto; Kaneko, Koji; Matsuda, Tatsuma; Galatanu, A.; Takeuchi, Tetsuya*; Hashimoto, Shin*; Ueda, Taiki*; Settai, Rikio*; Onuki, Yoshichika; Bernhoeft, N.*

Journal of Physics; Condensed Matter, 16(15), p.L207 - L212, 2004/04

 Times Cited Count:88 Percentile:5.9(Physics, Condensed Matter)

no abstracts in English

Journal Articles

Strong-coupling theory of superconductivity in a degenerate Hubbard model

Takimoto, Tetsuya; Hotta, Takashi; Ueda, Kazuo*

Physical Review B, 69(10), p.104504_1 - 104504_9, 2004/03

 Times Cited Count:130 Percentile:3.27(Materials Science, Multidisciplinary)

In order to discuss superconductivity in orbital degenerate systems, a microscopic Hamiltonian is introduced. Based on the degenerate model, a strong-coupling theory of superconductivity is developed within the fluctuation exchange (FLEX) approximation where spin and orbital fluctuations, spectra of electron, and superconducting gap function are self-consistently determined. Applying the FLEX approximation to the orbital degenerate model, it is shown that the $$d_{x^2-y^2}$$-wave superconducting phase is induced by increasing the orbital splitting energy which leads to the development and suppression of the spin and orbital fluctuations, respectively. It is proposed that the orbital splitting energy is a controlling parameter changing from the paramagnetic to the antiferromagnetic phase with the $$d_{x^2-y^2}$$-wave superconducting phase in between.

Journal Articles

Magnetic properties of U$$_2$$RhGa$$_8$$ and U$$_2$$FeGa$$_8$$

Ikeda, Shugo; Okubo, Tomoyuki*; Inada, Yoshihiko*; Tokiwa, Yoshifumi; Kaneko, Koji; Matsuda, Tatsuma; Yamamoto, Etsuji; Haga, Yoshinori; Onuki, Yoshichika

Journal of Physics; Condensed Matter, 15(28), p.S2015 - S2018, 2003/07

 Times Cited Count:6 Percentile:62.81(Physics, Condensed Matter)

no abstracts in English

Journal Articles

Superconductivity in the orbital degenerate model for heavy fermion systems

Takimoto, Tetsuya; Hotta, Takashi; Ueda, Kazuo*

Journal of Physics; Condensed Matter, 15(28), p.S2087 - S2093, 2003/07

 Times Cited Count:12 Percentile:44.23(Physics, Condensed Matter)

Rich physics is expected to appear due to the coupling between orbital and spin degrees of freedom in strongly correlated electron system with orbital degeneracy. Especially, it is considered that the superconducting transition in orbital degenerate system is one of the most interesting phenomena. For instance, triplet superconductivity occurs in Sr$$_2$$RuO$$_4$$ where three cylindrical Fermi surfaces are observed. Also, heavy fermion superconductors are considered to have potentially orbital degree of freedom due to large degeneracy of $$f$$-electron states. We discuss the effect of orbital fluctuations on superconductivity by using random phase approximation and fluctuation exchange (FLEX) approximation. It is also expected that the FLEX approximation is useful to study the correlation between spin and orbital fluctuations for the orbital degenerate system.

Journal Articles

Pressure effect on antiferromagnetic ordering in UPb$$_3$$

Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika; Nakashima, Miho*; Aoki, Dai*; Onuki, Yoshichika*; Hedo, Masato*; Uwatoko, Yoshiya*

Acta Physica Polonica B, 34(2), p.1239 - 1242, 2003/02

Uranium intermetallic compounds UX$$_3$$ (X = Si, Ge, Sn, Pb) form a ariety of magnetic properties including Pauli paramagnetism in USi$$_3$$ and UGe$$_3$$, spin fluctuations in USn$$_3$$ and antiferromagnetism in UPb$$_3$$. Among them, UPb$$_3$$ is an antiferromagnet below the N$'e$el temperature 32 K with a large electronic specific heat $$gamma$$ = 110 mJ/K$$^2$$mol. In this study we present the electrical resistivity measurement under high pressure up to 8 GPa. We found that at low pressure $$T_{rm N}$$ increases with increasing pressure. It has a maximum value 36 K at 3 GPa, then decreases with increasing pressure.In addition we observed an additional resistive anomaly followed by a steep decrease in resistivity below $$T_{rm N}$$ under pressure.The maximum pressure 8 GPa in the present study was not enough to suppress the antiferromagnetic transition.The critical pressure is estimated to be around 12 GPa.

Journal Articles

$$^{238}$$U M$"o$ssbauer study of UPt$$_{3}$$

Tsutsui, Satoshi; Nakada, Masami; Nasu, Saburo*; Haga, Yoshinori; Yamamoto, Etsuji; Kimura, Noriaki*; Onuki, Yoshichika

Journal of Magnetism and Magnetic Materials, 226-230(Part.1), p.87 - 88, 2001/05

no abstracts in English

Journal Articles

High-quality single crystal growth and neutron scattering experiments in the heavy fermion superconductor UPd$$_{2}$$Al$$_{3}$$

Haga, Yoshinori; Metoki, Naoto; Koike, Yoshihiro; Yamamoto, Etsuji; Onuki, Yoshichika

Journal of the Physical Society of Japan, Vol.70, Supplement A, p.25 - 27, 2001/05

 Times Cited Count:3 Percentile:71.54(Physics, Multidisciplinary)

no abstracts in English

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