Composite pairing in a mixed-valent two-channel Anderson model

Flint, Rebecca; Nevidomskyy, Andriy H.; Coleman, Piers

doi:10.1103/physrevb.84.064514

Cited by 29 publications

(30 citation statements)

References 31 publications

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“…In the present context of QPI theory the microscopic origin of the unconventional superconductivity is not an issue. For CeCoIn 5 , various proposals based on spin fluctuation theory 17,18 and composite pairing 19 have been advanced.…”

Section: Introductionmentioning

confidence: 99%

Quasiparticle interference in the heavy-fermion superconductorCeCoIn5

2011

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We investigate the quasiparticle interference in the heavy fermion superconductor CeCoIn 5 as a direct method to confirm the d-wave gap symmetry. The ambiguity between d xy and d x 2 −y 2 symmetry remaining from earlier specific heat and thermal transport investigations has been resolved in favor of the latter by the observation of a spin resonance that can occur only in d x 2 −y 2 symmetry. However, these methods are all indirect and depend considerably on theoretical interpretation. Here we propose that quasiparticle interference (QPI) spectroscopy by scanning tunneling microscopy (STM) can give a direct fingerprint of the superconducting gap in real space that may lead to a definite conclusion on its symmetry for CeCoIn 5 and related 115 compounds. The QPI pattern for both magnetic and nonmagnetic impurities is calculated for the possible d-wave symmetries and characteristic differences are found that may be identified by use of the STM method.

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Section: Introductionmentioning

confidence: 99%

Quasiparticle interference in the heavy-fermion superconductorCeCoIn5

2011

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“…Lastly, the key prediction of the composite pairing theory for a sharp NQR frequency shift upon entering the SC state 11,38 could not be verified.…”

Section: Discussionmentioning

confidence: 94%

“…Such a picture for the normal-state fluctuations in PuCoGa 5 would resemble, for example, the case of δ-Pu where the mixed-valence 5f states 12 are accompanied by well-defined spin fluctuations, as was recently revealed by inelastic neutron scattering 37 . An alternative theoretical approach puts forth a composite pairing mechanism, within the framework of a two-channel Anderson model 10,11,38 , aiming to provide an overarching microscopic description for heavy-fermion superconductivity. This theory predicts a sharp change in ν Q upon entering the SC state, due to redistribution of the f -electron charge within the unit cell 11,38 .…”

Section: 4mentioning

confidence: 99%

“…An alternative theoretical approach puts forth a composite pairing mechanism, within the framework of a two-channel Anderson model 10,11,38 , aiming to provide an overarching microscopic description for heavy-fermion superconductivity. This theory predicts a sharp change in ν Q upon entering the SC state, due to redistribution of the f -electron charge within the unit cell 11,38 . This effect has been well-documented in PuCoIn 5 30 and also observed in PuRhIn 5 39 , but we were not able to detect a similar appreciable shift of ν Q below T c in PuCoGa 5 .…”

Section: 4mentioning

confidence: 99%

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Extended nuclear quadrupole resonance study of the heavy-fermion superconductorPuCoGa5

et al. 2016

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PuCoGa5 has emerged as a prototypical heavy-fermion superconductor, with its transition temperature (Tc ≃ 18.5 K) being the highest amongst such materials. Nonetheless, a clear description as to what drives the superconducting pairing is still lacking, rendered complicated by the notoriously intricate nature of plutonium's 5f valence electrons. Here, we present a detailed 69,71 Ga nuclear quadrupole resonance (NQR) study of PuCoGa5, concentrating on the system's normal state properties near to Tc and aiming to detect distinct signatures of possible pairing mechanisms. In particular, the quadrupole frequency and spin-lattice relaxation rate were measured for the two crystallographically inequivalent Ga sites and for both Ga isotopes, in the temperature range 1.6 K -300 K. No evidence of significant charge fluctuations is found from the NQR observables. On the contrary, the low-energy dynamics is dominated by anisotropic spin fluctuations with strong, nearly critical, in-plane character, which are effectively identical to the case of the sister compound PuCoIn5. These findings are discussed within the context of different theoretical proposals for the unconventional pairing mechanism in heavy-fermion superconductors.

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“…Neutron inelastic scattering has failed to detect any sign of a resonance as found, for example, in the isostructural CeCoIn 5 compound [9], which also has d-wave symmetry, although the difficulty of performing these neutron experiments on Pu should not be overlooked. Recent theoretical efforts [10][11][12] have concluded that the driving mechanism for superconductivity is valence fluctuations. Electronic structure calculations combining the local-density approximation with an exact diagonalization of the Anderson impurity model [13] show an intermediate 5f 5 − 5f 6 -valence ground state and delocalization of the 5f 5 multiplet of the Pu atom 5f shell.…”

Section: Introductionmentioning

confidence: 99%

Thermal expansion of the heavy-fermion superconductor PuCoGa5

Eloirdi¹,

Giacobbe²,

Celdran³

et al. 2017

Phys. Rev. B

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We have performed high-resolution powder x-ray diffraction measurements on a sample of 242 PuCoGa5, the heavy-fermion superconductor with the highest critical temperature Tc = 18.7 K. The results show that the tetragonal symmetry of its crystallographic lattice is preserved down to 2 K. Marginal evidence is obtained for an anomalous behaviour below Tc of the a and c lattice parameters. The observed thermal expansion is isotropic down to 150 K, and becomes anisotropic for lower temperatures. This gives a c/a ratio that decreases with increasing temperature to become almost constant above ∼150 K. The volume thermal expansion coefficient αV has a jump at Tc, a factor ∼20 larger than the change predicted by the Ehrenfest relation for a second order phase transition. The volume expansion deviates from the curve expected for the conventional anharmonic behaviour described by a simple Grüneisen-Einstein model. The observed differences are about ten times larger than the statistical error bars but are too small to be taken as an indication for the proximity of the system to a valence instability that is avoided by the superconducting state.PACS numbers:

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Composite pairing in a mixed-valent two-channel Anderson model

Cited by 29 publications

References 31 publications

Quasiparticle interference in the heavy-fermion superconductorCeCoIn5

Quasiparticle interference in the heavy-fermion superconductorCeCoIn5

Extended nuclear quadrupole resonance study of the heavy-fermion superconductorPuCoGa5

Thermal expansion of the heavy-fermion superconductor PuCoGa5

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