Andreev reflections on heavy-fermion superconductors

Wilde, Yannick De; Heil, Joachim; Jansen, A. G. M.; Wyder, P.; Deltour, Robert; Aßmus, W.; Menovsky, A.A.; Sun, Wei; Taillefer, Louis

doi:10.1103/physrevlett.72.2278

Cited by 82 publications

(50 citation statements)

References 19 publications

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“…A significant deviation from the temperature dependence of the gap predicted for the BCS-type isotropic superconductor is observed. A depression of the gap is faster in our case similar to the measurements on UPt 3 [2].…”

supporting

confidence: 77%

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Superconducting energy gap in URu2Si2

Samuely

Szabó

Flachbart

et al. 1995

Physica B: Condensed Matter

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Superconducting energy gap in URu2Si2Samuely, P.; Szabo, P.; Flachbart, K.; Mihalik, M.; Menovsky, A.A. Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. The point-contact spectroscopy has been performed on the heavy fermion system URu2Si 2, where coexistence of antiferromagnetism and superconductivity occurs. The point contacts between a silver tip and polycrystalline URu2Si 2 have been studied in the temperature range from 100 mK to 20 K. On differential-conductance versus applied voltage traces the formation of a (pseudo)gap is observed below the N6el temperature T N = 17.5 K. This structure persists down to the lowest measured temperatures. Below the superconducting transition at T = 1.3 K a peak in the conductance emerges centered at the zero bias voltage due to the Andreev reflection on the superconducting energy gap. A compatibility of the observed superconducting energy gap with different kinds of symmetries is studied within the Blonder-Tinkham-Klapwijk theory.

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supporting

confidence: 77%

“…But results on the superconducting gap in URu2Si 2 (T c = 1.3 K) remains contradictory. Hasselbach et al [1] found their data slightly more compatible with the d-wave symmetry of the superconducting gap while De Wilde et al [2] highlighted the absence of zeros in a(k).…”

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confidence: 85%

Superconducting energy gap in URu2Si2

Samuely

Szabó

Flachbart

et al. 1995

Physica B: Condensed Matter

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“…The triangular-shaped PC Andreev-reflection spectra were recently observed by us in YFe Al 4 8 [6]. Earlier, similar behavior of the PC spectra was reported in [14] for the heavy-fermion UPt 3 . This behavior was attributed to the d-wave symmetry of the order parameter in the superconductor indicated.…”

supporting

confidence: 61%

Evidence for superconductivity and a pseudogap in the new magnetic compound PrAg6In6

Dmitriev

Rybaltchenko

Wyder

et al. 2005

Low Temperature Physics

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Direct evidence for superconductivity in the new magnetic compound PrAg 6 In 6 is revealed for the first time. The distinct Andreev-reflection current is observed in metallic point contacts (PC) based on this compound. The data obtained provide reason enough to suggest that the rise of superconductivity strongly depends on the local magnetic order varying over the sample volume. The triangular-shaped PC spectra (dV/dI V ( )) in the vicinity of the zero-bias voltage suggest an unconventional type of superconducting pairing. As follows from the temperature and magnetic field dependences of the PC spectra, the superconducting energy gap structure transforms into the pseudogap one as the temperature or the magnetic field increases. PACS: 74.70. Ad, 74.80.Fp According to the conventional views, only a perfect antiferromagnetic (AFM) order is well compatible with superconductivity in a quite broad temperature range. New magnetic superconductors whose magnetic structures are far from having perfect AFM order provide a new insight into the problem of interplay between magnetism and superconductivity. A few years ago, a new class of magnetic superconductors with the ThMn 12 -type crystal structure was perceived to exist. Radio-frequency impedance and heat capacity measurements carried out on several compounds of this family have revealed distinct features in the corresponding characteristics which might be associated with superconductivity in some regions of the samples. Such indications of superconductivity were found in

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“…In the latter case, the shape of this reduction should look like a double minimum characteristic, if an electron scattering at N-S boundary occurs, or should have a flat bottom when this scattering is absent. The triangular shape of spectrum may be caused by a magnetic pair-breaking scattering intrinsic in given compound or reflect the unconventional Cooperpairing, like in UPt 3 [10].…”

mentioning

confidence: 99%

Direct evidence for the occurrence of superconductivity in the magnetic compound YFe4Al8

Dmitriev

Rybaltchenko

Wyder

et al. 2002

Low Temperature Physics

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For the first time we present the direct evidence for superconductivity in the ternary magnetic compound YFe 4 Al 8 with the ThMn 12 type structure found via point-contact (PC) experiments on contacts between silver needle and single-crystal YFe 4 Al 8 , revealing the distinct Andreev-reflection current. The spectra measured prove the existence of normal-superconducting interface and exhibit the triangular-like shape in a vicinity of zero-bias voltage, inferring the unconventional type of superconductivity. The derived dependences of the order parameter versus temperature ∆(T) and magnetic field ∆(H) are presented. ∆(T) follows BCS theory, whereas ∆(H) do not satisfy any theoretical predictions. In some cases there exists noticeable superconductivity enhancement by a weak magnetic field. The data obtained imply the very inhomogeneous distribution of superconductivity over the sample volume in spite of its single crystal structure. We assume that the reason is associated with inherent magnetic inhomogeneities of this material. The highest values for the critical temperature T c , upper critical magnetic field H c2 , and ratio 2∆(0)/kT c are 7.4 K, 5 T, and 7.2, respectively. [3]. In this work we give, for the first time, the direct evidence for the existence of superconductivity in the rare-earth ternary magnetic compound YFe 4 Al 8 in an Andreevreflection experiment.The family of ternary magnetic compounds ReM 4 Al 8 (Re is a rare earth, M is a transition metal) with the ThMn 12 type structure is known for about two decade and their physical properties have been investigated extensively [4][5][6]. However, weak signs of superconductivity in some of the compounds belonging to this family were discovered only recently in the radio-frequency impedance and heat capacity experiments [7,8]. This is very surprising, because the compounds of this type have a

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Andreev reflections on heavy-fermion superconductors

Cited by 82 publications

References 19 publications

Superconducting energy gap in URu2Si2

Superconducting energy gap in URu2Si2

Evidence for superconductivity and a pseudogap in the new magnetic compound PrAg6In6

Direct evidence for the occurrence of superconductivity in the magnetic compound YFe4Al8

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