NMR and NQR Studies of Magnetism and Superconductivity in the Antiferromagnetic Heavy Fermion Superconductors UM<sub>2</sub>Al<sub>3</sub>(M=Ni and Pd)

Kyogaku, Masafumi; Kitaoka, Y.; Asayama, Kunisuke; Geibel, C.; Schank, C.; Steglich, F.

doi:10.1143/jpsj.62.4016

Cited by 100 publications

(54 citation statements)

References 21 publications

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“…This behavior is not compatible with isotropic s-wave gap. Rather, our result is qualitatively similar to that in other HF superconductors, such as CeCu 2 Si 2 [9], UBe 13 [22], etc [23,18], and also high-T c cuprate superconductors [24], which indicates that the SC energy gap is anisotropic. In terms of density of states (DOS), T 1s in the SC state is expressed as T1N T1s =…”

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confidence: 87%

Unique Spin Dynamics and Unconventional Superconductivity in the Layered Heavy Fermion CompoundCeIrIn5: NQR Evidence

et al. 2001

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We report measurements of the 115 In nuclear spin-lattice relaxation rate (1/T1) between T =0.09 K and 100 K in the new heavy fermion (HF) compound CeIrIn5. At 0.4 K ≤ T ≤ 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 +θ ) 3 4 variation with θ=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 T 3 variation, which suggests unconventional superconductivity with line-node gap. PACS: 74.25.Ha, 74.70Tx, 76.60.Gv The emergence of superconductivity near a magnetic instability in cerium (Ce)-based heavy fermion (HF) compounds is one of the most intriguing phenomena in strongly correlated electron systems. Except for CeCu 2 Si 2 which is superconducting at ambient pressure with T c =0. . In spite of efforts and progress, however, knowledge about this class of superconductors is still limited because of difficult experimental conditions. The recently discovered new family of Ce-based heavy electron systems, CeMIn 5 (M=Rh, Ir) with M=Ir being a superconductor already at ambient pressure [6,7], provides new opportunities for studying the nature of the superconductivity in the vicinity of a magnetic instability, the interplay between magnetic excitations and superconductivity, etc. In particular, CeIrIn 5 is suitable for studies using microscopic experimental probes that can be applied more easily at ambient pressure.CeMIn 5 (M=Rh, Ir) consists of alternating layers of CeIn 3 and MIn 2 . CeRhIn 5 is an antiferromagnet with T N =3.8 K but becomes superconducting below T c =2.1 K under pressures larger than 1.6 GPa [6]. In CeIrIn 5 , the resistivity is already zero at ambient pressure below 1.2 K, but the Meissner effect and the jump in the specific heat are found only at 0.4 K [7]. The electronic specific heat coefficient γ is found to be 750 mJ/mol K 2 [7], which suggests a large mass enhancement. Recent de Haas-van Alphen Oscillation in CeIrIn 5 also reveals a cyclotron mass that is ∼20 times larger than the band mass, consistent with the specific heat result [8].In this Letter, we report a measurement using local probe, the 115 In nuclear quadrupolar resonance (NQR) study in CeIrIn 5 down to 90 mK, at zero magnetic field.From the temperature (T ) dependence of the nuclear spin lattice relaxation rate (1/T 1 ), we find that CeIrIn 5 is much more itinerant than known Ce-compounds such as CeCu 2 Si 2 [9], and show that this compound is located near a magnetic ordering with anisotropic spin fluctuations due to the layered crystal structure. No anomaly was found at 1.2 K in the NQR quantities, but 1/T 1 shows an abrupt decrease at 0.40 K below which the NQR intensity also decreases as does the ac susceptibility, confirming a bulk superconductivity below T c =0.40 K. The lack of coherence peak in 1/T...

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confidence: 87%

Unique Spin Dynamics and Unconventional Superconductivity in the Layered Heavy Fermion CompoundCeIrIn5: NQR Evidence

et al. 2001

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“…12,13) Recent progress in the studies of ferromagnetic heavy-fermion superconductors such as UGe 2 , 14) URhGe, 15) and UIr, 16) and in particular UCoGe, 17) motivates researchers to seek for obtaining direct evidence for spin-triplet pairing. Among the organic superconductors, possible spintriplet pairing in quasi-one-dimensional superconductors (TMTSF) 2 X (X ¼ ClO 4 and PF 6 ) has been considered.…”

Section: Candidates Of Spin-triplet Superconductorsmentioning

confidence: 99%

Evaluation of Spin-Triplet Superconductivity in Sr₂RuO₄

et al. 2012

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This review presents a summary and evaluations of the superconducting properties of the layered ruthenate Sr 2 RuO 4 as they are known in the autumn of 2011. This paper appends the main progress that has been made since the preceding review by Mackenzie and Maeno was published in 2003. Here, special focus is placed on the critical evaluation of the spin-triplet, odd-parity pairing scenario applied to Sr 2 RuO 4 . After an introduction to superconductors with possible odd-parity pairing, accumulated evidence for the pairing symmetry of Sr 2 RuO 4 is examined. Then, significant recent progress on the theoretical approaches to the superconducting pairing by Coulomb repulsion is reviewed. A section is devoted to some experimental properties of Sr 2 RuO 4 that seem to defy simple explanations in terms of currently available spin-triplet scenario. The next section deals with some new developments using eutectic boundaries and micro-crystals, which reveals novel superconducting phenomena related to chiral edge states, odd-frequency pairing states, and half-fluxoid states. Some of these properties are intimately connected with the properties as a topological superconductor. The article concludes with a summary of knowledge emerged from the study of Sr 2 RuO 4 that are now more widely applied to understand the physics of other unconventional superconductors, as well as with a brief discussion of relatively unexplored but promising areas of ongoing and future studies of Sr 2 RuO 4 .KEYWORDS: Sr 2 RuO 4 , ruthenate, spin-triplet superconductivity, topological superconductor Spin-Triplet Superconductors Candidates of spin-triplet superconductorsIn the last three decades, and particularly since the discovery of high-transition-temperature (high-T c ) superconductivity of the cuprates, 1) studies of ''unconventional'' superconductivity have been one of the main topics in condensed-matter physics. Here we designate the term ''unconventional'' as the pairing based on non-phonon mechanisms.2) The unconventional superconductivity is mainly found in heavy-fermion superconductors (since 1978), 3) Unconventional superconductivity is characterized by the anisotropic gap function or order parameter which is integrated to be zero or a small value due to the variations of the wave function ''phase'', in contrast to an ordinary s-wave state. In many of them, including high-T c cuprates and iron pnictides, the electrons are clearly paired in spinsinglet states. In this point of view, they are similar to conventional s-wave superconductors, in which the spindegrees of freedom is lost in the charged superfluids. Spintriplet superfluid states are fully established in the Fermi liquid 3 He, 7,8) for which spin and mass supercurrents emerge in the charge-neutral superfluids. The question is then whether or not spin-triplet superconductors exist, and what novel superconducting properties they may exhibit due to their charge and spin supercurrents.There are several classes of candidates of spin-triplet superconductors represented in Table I. W...

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“…24(b). 9,92) On the other hand, ÉðrÞ with odd parity (p-wave) is not symmetric with respect to r, where the parallel spin state is shown in Fig. 24(c).…”

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confidence: 99%

Recent Advances in the Magnetism and Superconductivity of Heavy Fermion Systems

et al. 2004

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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.

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NMR and NQR Studies of Magnetism and Superconductivity in the Antiferromagnetic Heavy Fermion Superconductors UM₂Al₃(M=Ni and Pd)

Cited by 100 publications

References 21 publications

Unique Spin Dynamics and Unconventional Superconductivity in the Layered Heavy Fermion CompoundCeIrIn5: NQR Evidence

Unique Spin Dynamics and Unconventional Superconductivity in the Layered Heavy Fermion CompoundCeIrIn5: NQR Evidence

Evaluation of Spin-Triplet Superconductivity in Sr₂RuO₄

Recent Advances in the Magnetism and Superconductivity of Heavy Fermion Systems

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NMR and NQR Studies of Magnetism and Superconductivity in the Antiferromagnetic Heavy Fermion Superconductors UM2Al3(M=Ni and Pd)

Cited by 100 publications

References 21 publications

Unique Spin Dynamics and Unconventional Superconductivity in the Layered Heavy Fermion CompoundCeIrIn5: NQR Evidence

Unique Spin Dynamics and Unconventional Superconductivity in the Layered Heavy Fermion CompoundCeIrIn5: NQR Evidence

Evaluation of Spin-Triplet Superconductivity in Sr2RuO4

Recent Advances in the Magnetism and Superconductivity of Heavy Fermion Systems

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NMR and NQR Studies of Magnetism and Superconductivity in the Antiferromagnetic Heavy Fermion Superconductors UM₂Al₃(M=Ni and Pd)

Evaluation of Spin-Triplet Superconductivity in Sr₂RuO₄