Faculty Profiles - TEI Kokukei

Papers - TEI Kokukei

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

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

Impurity effect as a probe for the gap function in the filled skutterudite compound superconductor PrOs4Sb12: Sb-NQR study

M Nishiyama, T Kato, H Sugawara, D Kikuchi, H Sato, H Harima, GQ Zheng

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 74 ( 7 ) 1938 - 1941 2005.7

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

We have carried out nuclear quadrupole resonance (NQR) measurements in the filled skutterudite compounds Pr(Os1-x,Ru,)(4)Sb-12 (x = 0. 1, 0.2), in order to gain insights into the symmetry of the superconducting gap function. Upon replacing Os with Ru, the spin-lattice relaxation rate 1/T-1 becomes proportional to temperature (T) at low T far below T-c, and the magnitude of (1/T1T1)(low-T) increases with increasing Ru content. These results indicate that a finite density of states is induced at the Fermi level by the impurity, and thus suggest that there exist nodes in the gap function of PrOs4Sb12.

DOI： 10.1143/JPSJ.74.1938

Novel phase transition near the quantum critical point in the filled-skutterudite compound CeOs4Sb12: An Sb-NQR study

M Yogi, H Kotegawa, GQ Zhang, Y Kitaoka, S Ohsaki, H Sugawara, H Sato

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 74 ( 7 ) 1950 - 1953 2005.7

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

We report on a novel phase transition at T = 0.9 K in the Ce-based filled-skutterudite compound CeOs4Sb12 via measurements of the nuclear-spin lattice relaxation rate 1/T-1 and nuclear quadrupole resonance (NQR) spectrum of Sb nuclei. The temperature (T) dependence of]IT, behaves as if approaching closely an antiferromagnetic (AFM) quantum critical point (QCP), following the relation 1/T-1 proportional to T/(T - T-N)(1/2) with T-N = 0.06K in the range of T = 1.3-25K. The onset of either the spin-density-wave (SDW) or charge-density-wave (CDW) order at To = 0.9 K, that is, of the first order, is evidenced by a broadening of the NQR spectrum and a marked reduction in 1/T-1 just below T-0. The f-electron-derived correlated band realized in CeOs4Sb12 is demonstrated to give rise to the novel phase transition on the verge of AFM QCP.

DOI： 10.1143/JPSJ.74.1950

Superconductivity of the ternary boride Li2Pd3B probed by B-11 NMR

M Nishiyama, Y Inada, GQ Zheng

PHYSICAL REVIEW B 71 ( 22 ) 2005.6

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

We report a B-11 NMR measurement on the recently discovered superconductor Li2Pd3B. The nuclear spin lattice relaxation rate 1/T-1 shows a well-defined coherence peak just below T-c(H=1.46 T)=5.7 K, and the spin susceptibility measured by the Knight shift also decreases below T-c. These results indicate that the superconductivity is of conventional nature, with an isotropic gap. Our results also suggest that the p-electrons of boron and the d-electrons of palladium that hybridize with boron p-electrons are primarily responsible for the superconductivity.

DOI： 10.1103/PhysRevB.71.220505

Unconventional superconductivity near the antiferromagnetic criticality in CeCoIn5 : a study of In-115-NQR under pressure

M Yashima, S Kawasaki, Y Kawasaki, GQ Zheng, Y Kitaoka, H Shishido, R Settai, Y Haga, Y Onuki

PHYSICA B-CONDENSED MATTER 359 404 - 406 2005.4

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

We report on a systematic evolution of the superconducting (SC) characteristics of CeCoIn5 via nuclear-quadrupole-resonance (NQR) measurement under pressure (P). The application of P significantly suppresses the nuclear spin-lattice relaxation rate 1/T-1 that is dominated by antiferromagnetic (AFM) spin fluctuations (SFs). The marked suppression of AFM SFs leads to the reduction in the size of SC energy gap. Nevertheless, T-c increases with the pressure due to the increase in HF bandwidth. This is expected to make the lifetime of quasi-particles sufficiently long. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2005.01.080

Sb-121-NMR studies of single-crystal PrOs4Sb12

H Tou, M Doi, M Sera, M Yogi, Y Kitaoka, H Kotegawa, GQ Zheng, H Harima, H Sugawara, H Sato

PHYSICA B-CONDENSED MATTER 359 892 - 894 2005.4

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

Sb-121 nuclear magnetic resonance (NMR) measurements have been carried out on a single-crystalline PrOs4Sb12 for magnetic field (H) up to 15 T. A well-split Sb-121-NMR spectrum was observed for H parallel to < 0 0 1 >. We calculated the electric field gradient (EFG) of Sb site by a FLAPW method based on LDA. We have identified the observed NMR lines corresponding to three different Sb sites with asymmetric EFG tensors. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2005.01.254

In-115-NQR study of antiferromagnetism and superconductivity near magnetic criticality in CeIn3

S Kawasaki, T Mito, Y Kawasaki, H Kotegawa, GQ Zheng, Y Kitaoka, H Shishido, S Araki, R Settai, Y Onuki

PHYSICA B-CONDENSED MATTER 359 413 - 415 2005.4

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

We report the discovery of novel phases in CeIn3 on the verge of antiferromagnetism (AFM) through the In-nuclear quadrupole resonance (NQR) measurements. We have found that even though a pressure (P)-induced phase separation into AFM and paramagnetism (PM) takes place, a novel superconductivity (SC), which is induced without strong spin fluctuations, has been found to coexist with AFM on a microscopic level. We propose that the magnetic excitations such as spin-density fluctuations induced by the first-order magnetic phase transition might mediate attractive interaction to form Cooper pairs. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2005.01.083

Evidence for the microscopic coexistence of superconductivity and ferromagnetism in UGe2 : Ge-73-NMR/NQR study Reviewed

A Harada, H Kotegawa, Y Kawasaki, GQ Zheng, Y Kitaoka, E Yamamoto, Y Haga, Y Onuki, K Itoh, EE Haller

PHYSICA B-CONDENSED MATTER 359 1057 - 1059 2005.4

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

We report on the pressure-induced novel phases of ferromagnetism and superconductivity (SC) in the itinerant ferromagnet UGe2 via the Ge-73-NQR measurements under pressure (P). The NQR spectrum has revealed that the ferromagnetic phases are separated into weakly and strongly polarized phases around a critical value of P-c(*) similar to 1.2 GPa, pointing to a first-order transition around P-c(*). Here we present further evidence for the phase separation into ferromagnetic and paramagnetic phases around a critical pressure P-c similar to 1.6GPa. The measurements of nuclear spin-lattice relaxation rate 1/T-1 have probed that SC sets only in the ferromagnetic phase at T-sc similar to 0.2 K, but it does not in the paramagnetic phase. (c) 2005 Published by Elsevier B.V.

DOI： 10.1016/j.physb.2005.01.283

The phase diagram of antiferromagnetism and superconductivity in CeRhIn5: a study of In-115 NQR under pressure

S Kawasaki, M Yashima, T Mito, Y Kawasaki, GQ Zheng, Y Kitaoka, D Aoki, Y Haga, Y Onuki

JOURNAL OF PHYSICS-CONDENSED MATTER 17 ( 11 ) S889 - S893 2005.3

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

We report on the pressure (P) versus temperature (T) phase diagram of the P-induced heavy fermion (HF) superconductor CeRhIn5 via nuclear quadrupole resonance (NQR) measurements under P. At P = 2.1 GPa, the T dependence of the nuclear spin-lattice relaxation rate 1/T-1 revealed antiferromagnetic critical fluctuations due to the closeness of antiferromagnetism. As P decreases slightly down to 1.9 GPa, a pseudogap emerges above T-c similar to 2 K, suggesting the appearance of superconducting fluctuations associated with a strong coupling effect among quasiparticles.

DOI： 10.1088/0953-8984/17/11/019

Critical point and the nature of the pseudogap of single-layered copper-oxide Bi2Sr2-xLaxCuO6+delta superconductors

GQ Zheng, PL Kuhns, AP Reyes, B Liang, CT Lin

PHYSICAL REVIEW LETTERS 94 ( 4 ) 2005.2

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

We apply strong magnetic fields of H=28.5 to 43 T to suppress superconductivity (SC) in the cuprates Bi2Sr2-xLaxCuO6+delta (x=0.65, 0.40, 0.25, 0.15, and 0), and investigate the low temperature (T) normal state by Cu-63 nuclear spin-lattice relaxation rate (1/T-1) measurements. We find that the pseudogap (PG) phase persists deep inside the overdoped region but terminates at xsimilar to0.05, which corresponds to the hole doping concentration of approximately 0.21. Beyond this critical point, the normal state is a Fermi liquid that persists as the ground state when superconductivity is removed by the magnetic field. A comparison of the superconducting state with the H-induced normal state in the x=0.40 (T-c=32 K) sample indicates that there remains substantial part of the Fermi surface even in the fully developed PG state, which suggests that the PG and SC are coexisting matters.

DOI： 10.1103/PhysRevLett.94.047006

Magnetic criticality and unconventional superconductivity in CeCoIn5: Study of (115)in-nuclear quadrupole resonance under pressure

M Yashima, S Kawasaki, Y Kawasaki, GQ Zheng, Y Kitaoka, H Shishido, R Settai, Y Haga, Y Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73 ( 8 ) 2073 - 2076 2004.8

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

We report the systematic evolution of the superconducting (SC) characteristics of the heavy-fermion (HF) superconductor CeCoIn5 via nuclear-quadrupole-resonance (NQR) measurement under pressure (P). The application of P significantly suppresses the nuclear spin-lattice relaxation rate 1/T-1 that is dominated by antiferromagnetic (AFM) spin fluctuations (SFs) specific to a quantum critical point (QCP). It is demonstrated that the marked suppression of AFM SFs leads to a reduction in the SC energy gap or in the coupling strength of the Cooper pair. T-c,T- nevertheless, increases with increasing P due to the increase in HF bandwidth. This is expected to make the lifetime of quasi-particles sufficiently long.

DOI： 10.1143/JPSJ.73.2073

Coexistence of antiferromagnetic order and superconductivity in five-layered Hg-based high-T-c cuprate Reviewed

H Kotegawa, Y Kitaoka, Y Araki, Y Tokunaga, GQ Zheng, K Tokiwa, T Watanabe, A Iyo, H Kito, Y Tanaka, H Ihara

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 408 761 - 763 2004.8

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

We report a coexistence of superconductivity and antiferromagnetism in five-layered compound HgBa2Ca4Cu5Oy (Hg-1245) with T-c = 108 K, which is composed of two types of CuO2 planes in a unit cell, three inner planes (IP) and two outer planes (OP). The Cu-NMR study has revealed that the OP undergoes a superconducting (SC) transition at T-c = 108 K, whereas three underdoped IPs do an antiferromagnetic (AF) transition below T-N similar to 60 K with the Cu moments of similar to 0.3-0.4 mu(B). The metallic behavior observed at the IP well below T-N points to a possibility that SC and AF order parameters coexist in a single CuO2 plane. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2004.03.081

New superconducting and magnetic phases emerge on the magnetic criticality in CeIn3

S Kawasaki, T Mito, Y Kawasaki, H Kotegawa, GQ Zheng, Y Kitaoka, H Shishido, S Araki, R Settai, Y Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73 ( 7 ) 1647 - 1650 2004.7

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

We report the discovery of new superconducting and novel magnetic phases in CeIn3 on the verge of antiferromagnetism (AFM) under pressure (P) through the In-nuclear quadrupole resonance (NQR) measurements. We have found a P-induced phase separation of AFM and paramagnetism (PM) without any trace of a quantum phase transition in CeIn3. A new type of superconductivity (SC) was found, under P = 2.28-2.5 GPa, to coexist with AFM. It is magnetically separated from PM where the heavy fermion SC takes place. We propose that the magnetic excitations such as spin-density fluctuations induced by the first-order magnetic phase transition might mediate attractive interaction to form Cooper pairs.

DOI： 10.1143/JPSJ.73.1647

Coexistence of antiferromagnetic order and unconventional superconductivity in heavy-fermion CeRh1-xIrxIn5 compounds: Nuclear quadrupole resonance studies Reviewed

GQ Zheng, N Yamaguchi, H Kan, Y Kitaoka, JL Sarrao, PG Pagliuso, NO Moreno, JD Thompson

PHYSICAL REVIEW B 70 ( 1 ) 2004.7

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

We present a systematic In-115 NQR study on the heavy-fermion compounds CeRh1-xIrxIn5 (x=0.25, 0.35, 0.45, 0.5, 0.55, and 0.75). The results provide strong evidence for the microscopic coexistence of antiferromagnetic (AF) order and superconductivity (SC) in the range of 0.35less than or equal toxless than or equal to0.55. Specifically, for x=0.5, T-N is observed at 3 K with a subsequent onset of superconductivity at T-c=0.9 K. T-c reaches a maximum (0.94 K) at x=0.45 where T-N is found to be the highest (4.0 K). Detailed analysis of the measured spectra indicate that the same electrons participate in both SC and AF order. The nuclear spin-lattice relaxation rate 1/T-1 shows a broad peak at T-N and follows a T-3 variation below T-c, the latter property indicating unconventional SC as in CeIrIn5 (T-c=0.4 K). We further find that, in the coexistence region, the T-3 dependence of 1/T-1 is replaced by a T-linear variation below Tsimilar to0.4 K, with the value (T-1)(Tc)/(T-1)(low T) increasing with decreasing x, likely due to low-lying magnetic excitations associated with the coexisting magnetism.

DOI： 10.1103/PhysRevB.70.014511

Coexistence of antiferromagnetic order and unconventional superconductivity in heavy-fermion CeRh1-xIrxIn5 compounds: Nuclear quadrupole resonance studies Reviewed

Guo-Qing Zheng, N. Yamaguchi, H. Kan, Y. Kitaoka, J. L. Sarrao, P. G. Pagliuso, N. O. Moreno, J. D. Thompson

Physical Review B - Condensed Matter and Materials Physics 70 ( 1 ) 1 - 14511 2004.7

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

We present a systematic 115In NQR study on the heavy-fermion compounds CeRh1-xIrxIn5 (x=0.25, 0.35, 0.45, 0.5, 0.55, and 0.75). The results provide strong evidence for the microscopic coexistence of antiferromagnetic (AF) order and superconductivity (SC) in the range of 0.35≤x≤0.55. Specifically, for x=0.5, TN is observed at 3 K with a subsequent onset of superconductivity at Tc=0.9 K. Tc reaches a maximum (0.94 K) at x=0.45 where TN is found to be the highest (4.0 K). Detailed analysis of the measured spectra indicate that the same electrons participate in both SC and AF order. The nuclear spin-lattice relaxation rate 1/T1 shows a broad peak at TN and follows a T3 variation below Tc, the latter property indicating unconventional SC as in CeIrIn5 (Tc=0.4 K). We further find that, in the coexistence region, the T3 dependence of 1/T1 is replaced by a T-linear variation below T ∼0.4 K, with the value (T1)Tc/(T1)low T increasing with decreasing x, likely due to low-lying magnetic excitations associated with the coexisting magnetism.

DOI： 10.1103/PhysRevB.70.014511

Macroscopically inhomogeneous state at the boundary between the superconducting, antiferromagnetic, and metallic phases in quasi-one-dimensional (TMTSF)(2)PF6

AV Kornilov, VM Pudalov, Y Kitaoka, K Ishida, GQ Zheng, T Mito, JS Qualls

PHYSICAL REVIEW B 69 ( 22 ) 2004.6

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

We report on experimental studies of the phase state and the character of phase transitions in the quasi-one-dimensional organic compound (TMTSF)(2)PF6 in the close vicinity of the borders between the metal (M), antiferromagnetic (AF) insulator, and superconducting (SC) states. In order to drive the system precisely through the phase border P-0(T-0), the sample was maintained at fixed temperature T and pressure P, whereas the critical pressure P-0 was tuned by applying the magnetic field B. In this approach, the magnetic field was used (i) for smooth and precise tuning deltaP=P-P-0 [thanks to a monotonic P-0(B) dependence] and (ii) for identifying the phase composition (due to qualitatively different magnetoresistance behavior in different phases). Experimentally, we measured magnetoresistance R(B) and its temperature dependence R(B,T) in the pressure range 0-1 GPa. Our studies focus on the features of the magnetoresistance at the phase transitions between the M and AF phases and in the close vicinity to the superconducting transition at Tapproximate to1 K. We found pronounced history effects arising when the AF/M phase border is crossed by sweeping the magnetic field: the resistance depends on a trajectory which the system arrives at a given point of the P-B-T phase space. In the transition from the M to AF phase, driven by increasing magnetic field, the features of the M phase extend well into the AF phase. At the opposite transition from the AF to M phase, the features of the AF phase are observed in the M phase. These results evidence for a macroscopically inhomogeneous state, which contains macroscopic inclusions of the minority phase, spatially separated from the majority phase. When the system is driven away from the transition, the homogeneous state is restored; upon a return motion to the phase boundary, no signatures of the minority phase are observed up to the phase boundary.

DOI： 10.1103/PhysRevB.69.224404

Macroscopically inhomogeneous state at the boundary between the superconducting, antiferromagnetic, and metallic phases in quasi-one-dimensional (TMTSF)2PF6 Reviewed

A. V. Kornilov, V. M. Pudalov, Y. Kitaoka, K. Ishida, G. Q. Zheng, T. Mito, J. S. Qualls

Physical Review B - Condensed Matter and Materials Physics 69 ( 22 ) 1 - 224404 2004.6

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

We report on experimental studies of the phase state and the character of phase transitions in the quasi-one-dimensional organic compound (TMTSF) 2PF6 in the close vicinity of the borders between the metal (M), antiferromagnetic (AF) insulator, and superconducting (SC) states. In order to drive the system precisely through the phase border P 0(T0), the sample was maintained at fixed temperature T and pressure P, whereas the critical pressure P0 was tuned by applying the magnetic field B. In this approach, the magnetic field was used (i) for smooth and precise tuning δP = P - P0 [thanks to a monotonic P0(B) dependence] and (ii) for identifying the phase composition (due to qualitatively different magnetoresistance behavior in different phases). Experimentally, we measured magnetoresistance R(B) and its temperature dependence R(B,T) in the pressure range 0-1 GPa. Our studies focus on the features of the magnetoresistance at the phase transitions between the M and AF phases and in the close vicinity to the superconducting transition at T ≈ 1 K. We found pronounced history effects arising when the AF/M phase border is crossed by sweeping the magnetic field: the resistance depends on a trajectory which the system arrives at a given point of the P-B-T phase space. In the transition from the M to AF phase, driven by increasing magnetic field, the features of the M phase extend well into the AF phase. At the opposite transition from the AF to M phase, the features of the AF phase are observed in the M phase. These results evidence for a macroscopically inhomogeneous state, which contains macroscopic inclusions of the minority phase, spatially separated from the majority phase. When the system is driven away from the transition, the homogeneous state is restored
upon a return motion to the phase boundary, no signatures of the minority phase are observed up to the phase boundary.

DOI： 10.1103/PhysRevB.69.224404

Magnetism and superconductivity near the quantum criticality in CeRhIn5: In-115-NQR study under pressure

S. Kawasaki, T. Mito, Y. Kawasaki, G. -q. Zheng, Y. Kitaoka, D. Aoki, Y. Haga, Y. Onuki

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 272 E19 - E20 2004.5

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

We report a study on the interplay between antiferromagnetism (AFM) and superconductivity (SC) in CeRhIn5 under pressure P = 1.75 GPa: The onset of the magnetic order is evidenced from a clear split of In-115-NQR spectrum due to the spontaneous internal field below T-N = 2.5 K: Simultaneously, bulk SC is demonstrated by the observation of the Meissner diamagnetism signal whose size is the same as in the exclusively superconducting phase. These results indicate that the AFM coexists homogeneously with the SC at a microscopic level. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2003.11.122

Sb-NQR study of the "Kondo semiconductor'' CeOs4Sb12 Reviewed

M. Yogi, H. Kotegawa, G. -q. Zheng, Y. Kitaoka, S. Osaki, H. Sugawara, H. Sato

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 272 E45 - E46 2004.5

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

We report novel phase transition at similar to 0.9 K in the Ce-based filled-skutterudite compound CeOs4Sb12 via the measurements of nuclear-spin-lattice-relaxation-rate 1/T-1 and Sb-123-NQR spectrum. The temperature (T) dependence of 1/T-1 follows 1/T-1 proportional to (T-theta)(1/2) with theta = 0.06 K in the range of 1.3 K < T < 25 K, suggesting that the system is close to an antiferromagnetic critical point. The onset of spin-density-wave (SDW) order at T-SDW similar to 0.9 K is evidenced by the broadening of NQR spectrum and marked reduction in 1/T-1 just below TSDW: (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2003.12.448

Exotic superconductivity in the coexistent phase of antiferromagnetism and superconductivity in CeCu2(Si0.98Ge0.02)(2): A Cu-NQR study under hydrostatic pressure

Y Kawasaki, KJ Ishida, SJ Kawasaki, T Mito, GQ Zheng, Y Kitaoka, C Geibel, F Steglich

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73 ( 1 ) 194 - 197 2004.1

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

We report a pressure (P) effect on CeCu2(Si0.98Ge0.02)(2) where an antiferromagnetic (AFM) order at T-N similar to 0.75 K coexists with superconductivity below T-c similar to 0.4 K. At pressures exceeding P = 0.19 GPa, the AFM order is suppressed, which demonstrates that the sudden emergence of AFM order due to the Ge doping is ascribed to the intrinsic lattice expansion. The exotic superconductivity at P = 0 GPa is found to evolve into a typical heavy-fermion one with a line-node gap above P = 0.91 GPa. We highlight that the anomalous enhancement in nuclear spin-lattice relaxation rate 1/T-1, that follows a T1T = const. behavior well below T-c at P = 0 GPa is characterized by the persistence of low-lying magnetic excitations, which may be inherent to the coexistent state of antiferromagnetism and superconductivity.

DOI： 10.1143/JPSJ.73.194

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