Physical properties of the noncentrosymmetric superconductor Nb<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow /><mml:mrow><mml:mn>0</mml:mn><mml:mo>.</mml:mo><mml:mn>18</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>Re<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow /><mml:mrow><mml:mn>0</mml:mn><mml:mo>.</mml:mo><mml:mn>82</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Karki, Amar B.; Xiong, Yimin; Haldolaarachchige, Neel; Stadler, Shane; Vekhter, Ilya; Adams, P. W.; Young, David P.; Phelan, W. Adam; Chan, Julia Y.

doi:10.1103/physrevb.83.144525

Cited by 86 publications

(138 citation statements)

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“…The H c2 (T ) curve shows a positive curvature close to T c and is linear thereafter. A similar behavior has also been observed in polycrystalline borocarbides [18], MgB 2 [19,20], Nb 0.18 Re 0.82 [21], and Re 3 W [22] and is considered as a signature of multi-gap superconductivity. A conventional Werthamer-HelfandHohenberg model can not describe H c2 (T ) of Bi 4 O 4 S 3 .…”

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confidence: 48%

Low superfluid density and possible multigap superconductivity in theBiS2-based layered superconductorBi4O4S3

et al. 2013

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The magnetic penetration depth λ as a function of temperature in Bi4O4S3 was studied by muon-spin-spectroscopy measurements. The superfluid density of Bi4O4S3 is found to be very low. The dependence of λ −2 on temperature possibly suggests the existence of two s-wave type energy gaps with the zero-temperature values of 0.93(3) and 0.09(4) meV. The upturn in the temperature dependence of the upper critical field close to Tc further supports multi-gap superconductivity in Bi4O4S3. The presence of two superconducting energy gaps is consistent with theoretical and other experimental studies. However, a single-gap s-wave model fit with a gap of 0.88(2) meV can not be ruled out completely. The value of λ(T ) at T = 0 K is estimated to be λ(0) = 861(17) nm, one of the largest of all known layered superconductors, reflecting a very low superfluid density.PACS numbers: 74.25.Ha, 76.75.+i Recent years have witnessed a growing interest in superconductivity within layered crystal structure compounds. The recent discovery of superconductivity in the BiS 2 -based compound Bi 4 O 4 S 3 [1, 2] with a transition temperature (T c ) of ≈ 4.5 K has further fostered the research interest in layered superconductors. Exotic superconductivity with higher T c and/or with unconventional pairing mechanism has often been found in materials with a layered crystal structure. In this context, the most familiar examples are the high-T c cuprates and the Fe-based superconductors, where the corresponding CuO 2 or Fe 2 An 2 (An = P, As, Se, Te) layer plays an important role in determining the superconducting properties [3][4][5]. Similarly, the BiS 2 layer is believed to be the basic building block for inducing superconductivity in Bi 4 O 4 S 3 and it is expected that the doping mechanism resembles that of cuprates and Fe-based superconductors. This argument is supported by the discovery of other BiS 2 -based superconductors ReO 1−x F x BiS 2 (Re = La, Ce, Pr, and Nd) with T c values of 10.6, 3.0, 5.5, and 5.6 K, respectively [6][7][8][9].Up to now, only very few theoretical and experimental studies have been performed on Bi 4 O 4 S 3 . The parent phase (Bi 6 O 8 S 5 ) is a band insulator which becomes superconducting after electron doping [1]. A first principles band structure calculation indicates that the superconductivity in Bi 4 O 4 S 3 originates from two Bi 6p orbitals, as they intersect the Fermi surface [10]. A RPA analysis of a two-orbital model for the BiS 2 -based superconductors suggests that the spin fluctuations promote competing A 1g and B 2g superconducting states with similar pairing strengths [11]. Transport measurements under pressure reveal that T c of Bi 4 O 4 S 3 decreases monotonically without distinct change of the normal state metallic behavior [12]. The exact nature of the superconducting state is still debated. Hall, Seebeck coefficients, and magnetoresistance measurements suggest exotic multiband features in Bi 4 O 4 S 3 [13]. Recent measurements of the temperature dependence of the magnetic penetration depth λ us...

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confidence: 48%

Low superfluid density and possible multigap superconductivity in theBiS2-based layered superconductorBi4O4S3

et al. 2013

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“…The [6]. Since electronic correlations in studied here compounds are rather negligible [7], the value of electron-phonon enhancement factor, λ ep ≈ 0.5, derived from the relation: γ = γ e (1 + λ ep ), should be a reasonable estimation.…”

Section: Resultsmentioning

confidence: 99%

“…8 Nb 5.2 (T SC = 8.8 K [6]), and Re 24 Ti 5 (T SC = 5.8 K [7]) exhibits rather a BCS-like behaviour. This effect is believed to be related to the quality of polycrystalline samples used in particular studies or still too weak influence of the ASOC on bands forming the Fermi surface (FS) in this family of compounds [7].…”

Section: Introductionmentioning

confidence: 99%

“…The recent renewal of an interest in this family of compounds [5,6,7] is connected with a search of unusual properties of a superconducting state in non-centrosymmetric systems. The lack of spatial inversion symmetry leads to the antisymmetric spin-orbit coupling (ASOC) that lifts the Krammers degeneracy and may induce a mixture of spin singlet and triplet states in the superconducting phase [8,9,10,11].…”

Section: Introductionmentioning

confidence: 99%

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Electronic structure of non-centrosymmetric superconductors Re24(Nb;Ti)5 by ab initio calculations

Winiarski

2014

Journal of Alloys and Compounds

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Electronic structures of superconducting Re 24 Nb 5 and Re 24 Ti 5 have been calculated employing the full-potential local-orbital method within the density functional theory. The investigations were focused on the influence of the antisymmetric spin-orbit coupling on band structures and Fermi surfaces of these non-centrosymmetric systems. The predicted here density of states at the Fermi level for Re 24 Ti 5 is abnormally low with respect to that deduced from previous heat capacity measurements. This discrepancy suggests an intermediate coupled superconducting state in Re 24 Ti 5 . The differences between electronic properties of both compounds could explain more robust superconductivity in the Nb-based material.

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“…Using the McMillan equation (34), we calculate the electron-phonon coupling constant λ ep = 0.51. [For this calculation the Coulomb repulsion constant was taken as μ* = 0.13 (μ* = 0.13 falls in the range 0.1-0.15 used in the literature) (35).] Having both the electron-phonon coupling constant λ ep and the Sommerfeld coefficient γ , the density of states at the Fermi energy can be calculated from N(E F ) = 3γ/[π 2 k 2 B (1 + λ ep )].…”

Section: The Electronic Structure Of Regamentioning

confidence: 99%

Endohedral gallide cluster superconductors and superconductivity in ReGa ₅

Xie

Luo

Phelan

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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We present transition metal-embedded (T@Ga n ) endohedral Gaclusters as a favorable structural motif for superconductivity and develop empirical, molecule-based, electron counting rules that govern the hierarchical architectures that the clusters assume in binary phases. Among the binary T@Ga n endohedral cluster systems, Mo 8 Ga 41 , Mo 6 Ga 31 , Rh 2 Ga 9 , and Ir 2 Ga 9 are all previously known superconductors. The well-known exotic superconductor PuCoGa 5 and related phases are also members of this endohedral gallide cluster family. We show that electron-deficient compounds like Mo 8 Ga 41 prefer architectures with vertex-sharing gallium clusters, whereas electron-rich compounds, like PdGa 5 , prefer edge-sharing cluster architectures. The superconducting transition temperatures are highest for the electron-poor, corner-sharing architectures. Based on this analysis, the previously unknown endohedral cluster compound ReGa 5 is postulated to exist at an intermediate electron count and a mix of corner sharing and edge sharing cluster architectures. The empirical prediction is shown to be correct and leads to the discovery of superconductivity in ReGa 5 . The Fermi levels for endohedral gallide cluster compounds are located in deep pseudogaps in the electronic densities of states, an important factor in determining their chemical stability, while at the same time limiting their superconducting transition temperatures. Although one can analyze the superconductivity, once discovered, through materials physics-based "k-space" pictures based on Fermi surfaces, energy band dispersions, and effective interactions, often it is chemists, whose viewpoint is instead from "real space" rather than k-space, who find such superconductors in the first place (1, 2). Given the difficulty in making extrapolations between the physics of superconductivity and the chemical stability of compounds that will be superconducting, there are as many strategies for finding new superconductors as there are researchers looking for them (3-5). Most such search strategies fail, because the interactions that give rise to superconductivity can also lead to competing electronic states or can be strong enough to tear potential compounds apart (6, 7).One chemical perspective for increasing the odds of finding superconductivity is to postulate that it runs in structural families. The perovskites are a well-known example of this in metal oxides, and in intermetallic compounds, the "122" ThCr 2 Si 2 structure type is a good example (8-10). It is the discovery of these new structural families of superconductors that often leads, sometimes slowly or sometimes quickly, to advances in new superconducting materials. Here we show that a previously unappreciated chemical family, the endohedral gallium cluster phases, is a favored chemical family for superconductivity. Further, we analyze the occurrence and hierarchical structures of such phases from a molecular perspective and then use that perspective to predict the existence and structure of a previously un...

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Physical properties of the noncentrosymmetric superconductor Nb0.18Re0.82

Cited by 86 publications

References 51 publications

Low superfluid density and possible multigap superconductivity in theBiS2-based layered superconductorBi4O4S3

Low superfluid density and possible multigap superconductivity in theBiS2-based layered superconductorBi4O4S3

Electronic structure of non-centrosymmetric superconductors Re24(Nb;Ti)5 by ab initio calculations

Endohedral gallide cluster superconductors and superconductivity in ReGa ₅

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Physical properties of the noncentrosymmetric superconductor Nb0.18Re0.82

Cited by 86 publications

References 51 publications

Low superfluid density and possible multigap superconductivity in theBiS2-based layered superconductorBi4O4S3

Low superfluid density and possible multigap superconductivity in theBiS2-based layered superconductorBi4O4S3

Electronic structure of non-centrosymmetric superconductors Re24(Nb;Ti)5 by ab initio calculations

Endohedral gallide cluster superconductors and superconductivity in ReGa 5

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Endohedral gallide cluster superconductors and superconductivity in ReGa ₅