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Featured researches published by Yoshinori Haga.


Journal of the Physical Society of Japan | 2006

Pressure-Induced Heavy-Fermion Superconductivity in Antiferromagnet CeIrSi3 without Inversion Symmetry

Ichiro Sugitani; Yusuke Okuda; Hiroaki Shishido; T. Yamada; A. Thamizhavel; Etsuji Yamamoto; Tatsuma D. Matsuda; Yoshinori Haga; Tetsuya Takeuchi; Rikio Settai; Yoshichika Onuki

We report the discovery of pressure-induced superconductivity in an antiferromagnet CeIrSi 3 , which lacks inversion symmetry in the tetragonal crystal structure. The Neel temperature T N = 5.0 K at ambient pressure decreases monotonically with increasing pressure, and becomes zero at about 2.5 GPa. Superconductivity appears in a wide pressure region from 1.8 GPa to about 3.5 GPa, with a relatively large superconduting transition temperature T sc = 1.6 K and a large upper critical field H c2 (0) = 11.1 T at 2.5 GPa, indicating heavy-fermion superconductivity.


Journal of the Physical Society of Japan | 2002

Fermi Surface, Magnetic and Superconducting Properties of LaRhIn5 and CeTIn5 (T: Co, Rh and Ir)

H. Shishido; Rikio Settai; Dai Aoki; Shugo Ikeda; Hirokazu Nakawaki; Noriko Nakamura; Tomoya Iizuka; Yoshihiko Inada; Kiyohiro Sugiyama; Tetsuya Takeuchi; K. Kindo; Tatsuo C. Kobayashi; Yoshinori Haga; Hisatomo Harima; Yuji Aoki; Takahiro Namiki; Hideyuki Sato; Yoshichika Onuki

We have studied Fermi surface properties of LaRhIn 5 and CeTIn 5 (T: Co, Rh and Ir) via the de Haas–van Alphen (dHvA) experiment. The Fermi surface of a non-4 f reference compound LaRhIn 5 is quasi...


Journal of the Physical Society of Japan | 2004

Recent Advances in the Magnetism and Superconductivity of Heavy Fermion Systems

Yoshichika Onuki; Rikio Settai; Kiyohiro Sugiyama; Tetsuya Takeuchi; Tatsuo C. Kobayashi; Yoshinori Haga; Etsuji Yamamoto

We present recent advances in the magnetism and superconductivity of rare earth and uranium compounds. Heavy fermions are formed on the basis of the competition between the RKKY interaction and the Kondo effect in these compounds. The application of pressure to these compounds is useful to control the electronic states in the antiferromagnets CeRh 2 Si 2 and CeRhIn 5 , and the ferromagnet UGe 2 . The quadrupole interaction or the quadrupole Kondo effect is found to be responsible for heavy fermions in PrFe 4 P 12 . A rich variety of superconducting properties are demonstrated: superconductivity of CeCoIn 5 and CeRhIn 5 in the vicinity of a quantum critical point, coexistence of ferromagnetism and superconductivity in UGe 2 , and superconductivity based on the quadrupole fluctuations in PrOs 4 Sb 12 , together with the relation between the superconducting transition temperature and the quasi-two dimensionality of the electronic states.


Journal of the Physical Society of Japan | 2004

Pressure-induced superconductivity in UIr

Teruhiko Akazawa; Hiroyuki Hidaka; Hisashi Kotegawa; Tatsuo C. Kobayashi; Tabito Fujiwara; Etsuji Yamamoto; Yoshinori Haga; Rikio Settai; Yoshichika Onuki

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 ...


Science | 2011

Rotational Symmetry Breaking in the Hidden-Order Phase of URu2Si2

Ryuji Okazaki; T. Shibauchi; H. J. Shi; Yoshinori Haga; Tatsuma D. Matsuda; Etsuji Yamamoto; Yoshichika Onuki; Hiroaki Ikeda; Y. Matsuda

The mysterious hidden-order phase of a heavy-fermion compound may be an electronic nematic state. A second-order phase transition is characterized by spontaneous symmetry breaking. The nature of the broken symmetry in the so-called “hidden-order” phase transition in the heavy-fermion compound URu2Si2, at transition temperature Th = 17.5 K, has posed a long-standing mystery. We report the emergence of an in-plane anisotropy of the magnetic susceptibility below Th, which breaks the four-fold rotational symmetry of the tetragonal URu2Si2. Two-fold oscillations in the magnetic torque under in-plane field rotation were sensitively detected in small pure crystals. Our findings suggest that the hidden-order phase is an electronic “nematic” phase, a translationally invariant metallic phase with spontaneous breaking of rotational symmetry.


Physical Review Letters | 2001

Unique Spin Dynamics and Unconventional Superconductivity in the Layered Heavy Fermion Compound CeIrIn5: NQR Evidence

G.-q. Zheng; K. Tanabe; T. Mito; Shinji Kawasaki; Y. Kitaoka; Dai Aoki; Yoshinori Haga; Yoshichika Onuki

We report measurements of the 115In nuclear spin-lattice relaxation rate ( 1/T1) between T = 0.09 and 100 K in the new heavy fermion (HF) compound CeIrIn5. At 0.4 < or = T< or = 100 K, 1/T1 is strongly T-dependent, which indicates that CeIrIn5 is much more itinerant than known Ce-based HFs. We find that 1/T1T, subtracting that for LaIrIn5, follows a (1 / T+straight theta)3/4 variation with straight theta = 8 K. We argue that this novel feature points to anisotropic, due to a layered crystal structure, spin fluctuations near a magnetic ordering. The bulk superconductivity sets in at 0.40 K below which the coherence peak is absent and 1/T1 follows a T3 variation, which suggests unconventional superconductivity with line-node gap.


Physical Review Letters | 2004

Evidence for a novel state of superconductivity in noncentrosymmetric CePt3Si: a 195Pt-NMR study.

M. Yogi; Y. Kitaoka; Hashimoto S; Yasuda T; Rikio Settai; Tatsuma D. Matsuda; Yoshinori Haga; Y. Onuki; P. Rogl; E. Bauer

We report on novel antiferromagnetic (AFM) and superconducting (SC) properties of noncentrosymmetric CePt3Si through measurements of the 195Pt nuclear spin-lattice relaxation rate 1/T(1). In the normal state, the temperature (T) dependence of 1/T(1) unraveled the existence of low-lying levels in crystal-electric-field multiplets and the formation of a heavy-fermion (HF) state. The coexistence of AFM and SC phases that emerge at T(N)=2.2 K and T(c)=0.75 K, respectively, takes place on a microscopic level. CePt3Si is the first HF superconductor that reveals a peak in 1/T(1) just below T(c) and, additionally, does not follow the T3 law that used to be reported for most unconventional HF superconductors. We remark that this unexpected SC characteristic may be related to the lack of an inversion center in its crystal structure.


Physical Review Letters | 2007

Exotic superconducting properties in the electron-hole-compensated heavy-fermion "Semimetal" URu2Si2.

Y. Kasahara; T. Iwasawa; Hiroaki Shishido; T. Shibauchi; Kamran Behnia; Yoshinori Haga; Tatsuma D. Matsuda; Yoshichika Onuki; Manfred Sigrist; Y. Matsuda

We show that the charge and thermal transport measurements on ultraclean crystals of URu2Si2 reveal a number of unprecedented superconducting properties. The uniqueness is best highlighted by the peculiar field dependence of thermal conductivity including the first-order transition at Hc2 with a reduction of entropy flow. This is a consequence of multiband superconductivity with compensated electronic structure in the hidden order state of this system. We provide strong evidence for a new type of unconventional superconductivity with two distinct gaps having different nodal topology.


Review of Scientific Instruments | 2009

Evaluations of pressure-transmitting media for cryogenic experiments with diamond anvil cell.

Naoyuki Tateiwa; Yoshinori Haga

The fourteen kinds of pressure-transmitting media were evaluated by the ruby fluorescence method at room temperature, 77 K using the diamond anvil cell (DAC) up to 10 GPa in order to find appropriate media for use in low temperature physics. The investigated media are a 1:1 mixture by volume of Fluorinert FC-70 and FC-77, Daphne 7373 and 7474, NaCl, silicon oil (polydimethylsiloxane), Vaseline, 2-propanol, glycerin, a 1:1 mixture by volume of n-pentane and isopentane, a 4:1 mixture by volume of methanol and ethanol, petroleum ether, nitrogen, argon, and helium. The nonhydrostaticity of the pressure is discussed from the viewpoint of the broadening effect of the ruby R(1) fluorescence line. The R(1) line basically broadens above the liquid-solid transition pressure at room temperature. However, the nonhydrostatic effects do constantly develop in all the media from the low-pressure region at low temperature. The relative strength of the nonhydrostatic effects in the media at the low temperature region is discussed. The broadening effect of the ruby R(1) line in the nitrogen, argon, and helium media are significantly small at 77 K, suggesting that the media are more appropriate for cryogenic experiments under high pressure up to 10 GPa with the DAC. The availability of the three media was also confirmed at 4.2 K.


Journal of the Physical Society of Japan | 2001

Unconventional Superconductivity in CeCoIn5 Studied by the Specific Heat and Magnetization Measurements

Shugo Ikeda; Hiroaki Shishido; Miho Nakashima; Rikio Settai; Dai Aoki; Yoshinori Haga; Hisatomo Harima; Yuji Aoki; Takahiro Namiki; Hideyuki Sato; Yoshichika Onuki

We measured the low-temperature specific heat in magnetic fields up to 80 kOe, together with the magnetization for the heavy-fermion superconductor CeCoIn 5 with the transition temperature T c = 2....

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Etsuji Yamamoto

Japan Atomic Energy Agency

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Y. Ōnuki

University of the Ryukyus

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Tatsuma D. Matsuda

Tokyo Metropolitan University

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E. Yamamoto

Japan Atomic Energy Research Institute

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