Full-Gap Superconductivity Robust against Disorder in Heavy-Fermion 
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>CeCu</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mi>Si</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Takenaka, Takaaki; Mizukami, Y.; Wilcox, J. A.; Kończykowski, M.; Seiro, S.; Geibel, C.; Tokiwa, Yutaka; Kasahara, Yuichi; Putzke, Carsten; Matsuda, Yuji; Carrington, A.; Shibauchi, T.

doi:10.1103/physrevlett.119.077001

Cited by 44 publications

(24 citation statements)

References 34 publications

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“…Conceptually, this process is somewhat analogous to the theory of meson mediated attractive nuclear force, except here the attraction commences between onsite electrons. We formulate the corresponding theory of superconductivity, and find excellent agreement with the recently observed fully gap, constant sign gap features in CeCu 2 Si 2 , [19][20][21][22][23][24][25] as well as in the Yb-doped CeCoIn 5 superconductors [40]. We predict definite relationship between SC T c and valence fluctuation (coherence) temperature T K , and other unique properties of the present theory.…”

Section: Introductionsupporting

confidence: 81%

“…[22] Furthermore, the observed robustness of superconductivity to disorder supports the absence of sign-reversal in the pairing symmetry scenario. [23,25] These results collectively signal towards a conventional, isotropic pairing symmetry in CeCu 2 Si 2 . CeCu 2 Si 2 has an interesting phase diagram exhibiting two SC domes under pressure, with an antiferromagnetic (AFM) quantum critical point (QCP) intercepting the first SC dome, while a possible valence fluctuation critical point lying beneath the second dome.…”

Section: Introductionmentioning

confidence: 74%

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Novel attractive pairing interaction in strongly correlated superconductors

Adhikary

Das

2019

SciPost Phys.

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Conventional and unconventional superconductivity, respectively, arise from attractive (electron-phonon) and repulsive (many-body Coulomb) interactions with fixed-sign and sign-reversal pairing symmetries. Although heavy-fermions, cuprates, and pnictides are widely believed to be unconventional superconductors, recent evidence in the former materials indicate the presence of a novel conventional type pairing symmetry beyond the electron-phonon coupling. We present a new mechanism of attractive potential between electrons, mediated by emergent gauge fields (vacuum or holon) in the strongly correlated mixed valence compounds. In the strong coupling limit, localized electron sites are protected from double occupancy, which results in an emergent holon guage fields. The holon states can, however, attract conduction electrons through valence fluctuation channel, and the resulting doubly occupied states with local and conduction electrons condensate as Cooper pairs with onsite, fixed-sign, s-wave pairing symmetry. We develop the corresponding self-consistent theory of superconductivity, and compare the results with experiments. Our theory provides a new mechanism of superconductivity whose applicability extends to the wider class of intermetallic/mixed-valence materials and other flat-band metals. arXiv:1906.01312v1 [cond-mat.supr-con]

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Section: Introductionsupporting

confidence: 81%

Section: Introductionmentioning

confidence: 74%

Novel attractive pairing interaction in strongly correlated superconductors

Adhikary

Das

2019

SciPost Phys.

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“…In clean superconductors, λ(0) is given by the equation 1/λ 2 (0) = µ 0 n s e 2 /m * , where n s is the superconducting electron density and m * is the effective mass of carriers. Therefore the long λ(0) leads to the possibilities of a low carrier density [27][28][29] and/or a heavy effective mass [30][31][32]. In contrast to these possibilities, the carrier density and the effective mass in the calculations are estimated as n = 9.0 × 10 21 cm −3 and m * = 0.68m e , respectively.…”

mentioning

confidence: 92%

Evidence for s -wave pairing with atomic scale disorder in the van der Waals superconductor NaSn2As2

et al. 2018

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The recent discovery of superconductivity in NaSn2As2 with a van der Waals layered structure raises immediate questions on its pairing mechanism and underlying electronic structure. Here, we present measurements of the temperature-dependent magnetic penetration depth λ(T ) in single crystals of NaSn2As2 down to ∼ 40 mK. We find a very long penetration depth λ(0) = 960 nm, which is strongly enhanced from the estimate of first-principles calculations. This enhancement comes from a short mean free path ℓ ≈ 1.7 nm, indicating atomic scale disorder possibly associated with the valence-skipping states of Sn. The temperature dependence of superfluid density is fully consistent with the conventional fully gapped s-wave state in the dirty limit. These results suggest that NaSn2As2 is an ideal material to study quantum phase fluctuations in strongly disordered superconductors with its controllable dimensionality.

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“…These conditions can be met by using δn s0 (T ) as a temperature dependent mean-field function and writing the power series in Eqs. (24,25) as…”

Section: A Renomalization Of Specific Heatmentioning

confidence: 99%

Renormalizations in unconventional superconducting states born of normal and singular Fermi liquids

Miyake¹,

Varma

2018

Phys. Rev. B

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The density of low energy particle-hole excitations is non-analytic in a singular Fermi-liquid, but it is altered on entering a superconducting state in which, in the pure limit, it vanishes asymptotically at the chemical potential and in general is analytic. The single-particle excitations in the superconducting states are then quasi-particles so that a form of Landau theory may be constructed for thermodynamic and transport properties in the superconducting state. In this theory, the renormalization of measurable properties due to quasi-particle interactions, such as specific heat, compressibility, magnetic susceptibility, superfluid density, etc. changes in a temperature dependent fashion from the non-interacting theory. This is illustrated by showing the renormalization of these quantities and the relation between the parameters introduced to account for their temperature dependence. When the renormalizations in the normal state are large or singular, temperature dependence of properties in the superconducting states are then in general not useful for identifying the nodal character or symmetry of the superconducting state except for measurements at very low temperatures, upper limits of which are specified. The results obtained are expected to be useful in interpreting the experimental results for the temperature dependence of various properties in the superconducting state born of singular Fermi liquids.

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Full-Gap Superconductivity Robust against Disorder in Heavy-Fermion CeCu2Si2

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Cited by 44 publications

References 34 publications

Novel attractive pairing interaction in strongly correlated superconductors

Novel attractive pairing interaction in strongly correlated superconductors

Evidence for s -wave pairing with atomic scale disorder in the van der Waals superconductor NaSn2As2

Renormalizations in unconventional superconducting states born of normal and singular Fermi liquids

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