Superconductivity at 5 K in NdO0.5F0.5BiS2

Jha, Rajveer; Kumar, Amitabh; Singh, Shiva Kumar; Awana, V. P. S.

doi:10.1063/1.4790322

Cited by 93 publications

(96 citation statements)

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“…A nearly 100% superconducting volume is observed for x = 0.3 while it is reduced to 70% for x = 0.5. The NdO 1−x F x BiS 2 system possesses a very small lower critical filed (µ 0 H c1 (0) ≈ 25 Oe) 19 , thus a tiny external magnetic field may significantly broaden the superconducting transition, as shown in Fig. 1(b).…”

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confidence: 99%

“…The magnetic penetration depth is proportional to the shift of the resonant frequency ∆ f (T ), i.e., λ(T ) = G∆ f (T )+λ(0), where the G factor is solely determined by the sample and coil geometries 18 and λ(0) is the penetration depth at zero temperature. The coil of the oscillator generates a tiny ac magnetic field (µ 0 H ac ≈ 20 mOe), which is much smaller than the lower critical field of NdO 1−x F x BiS 2 , 19 ensuring that the measurements were performed in a Meissner state. The electrical resistivity and magnetic susceptibility were measured in a commercial Physical Properties Measurement System (PPMS) and Magnetic Properties Measurement System (MPMS), respectively.…”

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Evidence for nodeless superconductivity in NdO_1−xF_xBiS₂(x= 0.3 and 0.5) single crystals

Jiao

Weng

Liu

et al. 2015

J. Phys.: Condens. Matter

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We measure the magnetic penetration depth ∆λ(T ) for NdO 1−x F x BiS 2 (x = 0.3 and 0.5) using the tunnel diode oscillator technique. The ∆λ(T ) shows an upturn in the low-temperature limit which is attributed to the paramagnetism of Nd ions. After subtracting the paramagnetic contributions, the penetration depth ∆λ(T ) follows exponential-type temperature dependence at T ≪ T c . Both ∆λ(T ) and the corresponding superfluid density ρ s (T ) can be described by the BCS model with an energy gap of ∆(0) ≈ 2.0 k B T c for both x = 0.3 and 0.5, suggesting strong-coupling BCS superconductivity in the presence of localized moments for NdO 1−x F x BiS 2 .PACS numbers: 74.70. Xa, 74.20.Rp The newly discovered superconductivity (SC) in Bi 4 O 4 S 3 1,2 and LnO 1−x F x BiS 2 (Ln = La, Ce, Pr, Nd and Yb) 3-7 has attracted considerable attentions in the community. These compounds crystalize in a layered crystal structure which is composed of an alternative stacking of the BiS 2 double layers and the LnO blocking layer. Electron or hole doping into the LnO layers may induce SC from a semiconducting parent compound 7 . Furthermore, recent measurements revealed a large upper critical field µH c2 (0) and strong superconducting fluctuations above T c in some of these superconductors 8,9 . These features are analogous to those of high T c cuprates 10 and the iron-based superconductors 11 and, therefore, unconventional SC with a possible high T c transition was expected in the BiS 2 -based compounds. On the other hand, no magnetic order has been revealed in the parent compounds [3][4][5][6] . Instead, a charge-density-wave (CDW) instability, which favors the conventional electron-phonon pairing mechanism, was theoretically discussed. 12 More recently, coexistence of spin-singlet and spin-triplet paring states 13 as well as a g-wave pairing state 14 were proposed for the BiS 2 -based superconductors; the former one arises from the strong spin-orbit coupling while the the latter one is presumably driven by electron-electron correlations.

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Evidence for nodeless superconductivity in NdO_1−xF_xBiS₂(x= 0.3 and 0.5) single crystals

Jiao

Weng

Liu

et al. 2015

J. Phys.: Condens. Matter

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“…Metallic behavior is observed for x ≥ 0.05. For typical REO1-xFxBiS2 [2,[16][17][18][19]35], a metallic behavior is not observed in resistivity-temperature (-T) characteristics, and a semiconducting-like behavior is observed, in spite of carrier doping by F substitutions. In contrast, for LaO1-xFxBiSSe, a metallic behavior is observed in the -T measurements for all electron-doped samples (x = 0.05-0.5).…”

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“…The in-plane chemical pressure is related to the orbital overlaps between Bi and Ch and can be tuned by element substitutions at the blocking layer or the conducting layer. For example, in REO0.5F0.5BiS2, isovalent substitution of La 3+ (at the RE site) by smaller Pr 3+ , Nd 3+ , or Sm 3+ induces bulk superconductivity [17][18][19][20], and Tc reaches above 5 K in NdO0.5F0.5BiS2 or Nd1-xSmxO0.5F0.5BiS2 [17,22]. Basically, the RE 3+ substitution does not affect the structural symmetry but compresses Bi-S planes along the in-plane direction.…”

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“…In semiconducting-like samples of LaO0.5F0.5BiS2, bulk superconductivity is not observed, while weak (filamentary) superconductivity is observed. To induce bulk superconductivity in the LaO0.5F0.5BiS2 system, external pressure effects [9][10][11][12][13][14][15][16] and/or element substitution at the La site [17][18][19][20], which optimize the crystal structure, are available. Namely, both electron carrier doping and crystal structure optimization are required for the emergence of bulk superconductivity in the BiCh2-based system.…”

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Intrinsic Phase Diagram of Superconductivity in the BiCh₂-Based System Without In-Plane Disorder

et al. 2017

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We have investigated the crystal structure and physical properties of LaO1-xFxBiSSe to reveal the intrinsic superconductivity phase diagram of the BiCh2-based layered compound family. From synchrotron X-ray diffraction and Rietveld refinements with anisotropic displacement parameters, we clearly found that the in-plane disorder in the BiSSe layer was fully suppressed for all x. In LaO1-xFxBiSSe, metallic conductivity and superconductivity are suddenly induced by electron doping even at x = 0.05 and 0.1 with a monoclinic structure. In addition, x (F concentration) dependence of the transition temperature (Tc) for x = 0.2-0.5 with a tetragonal structure shows an anomalously flat phase diagram. With these experimental facts, we have proposed the intrinsic phase diagram of the ideal BiCh2-based superconductors with less in-plane disorder.Since the discovery of Bi4O4S3 and REO1-xFxBiS2 (RE: rare earth) superconductors, BiCh2-based (Ch: chalcogen) superconductors have been drawing much attention as a new class of layered superconductors [1][2][3]. Since the crystal structure composed of alternate stacks of the electrically conducting BiCh2 layers and the insulating (blocking) layers resembles those of the Cuprate and the FeAs-based high-transition-temperature (high-Tc) superconductors [4,5], many experimental and theoretical studies have been performed to clarify the superconductivity mechanisms of this system and to increase Tc. However, the mechanisms have not been understood completely. Recently, Morice et al. proposed that a 2 weak-coupling electron-phonon mechanism cannot explain the emerging Tc, as high as 11 K, in the BiCh2-based systems, from first principle calculations [6]. Therefore, full understandings of the basic characteristics of the superconductivity in the BiCh2-based system are crucial.The parent phase of the BiCh2-based superconductor is a band insulator [1,7,8]. On the basis of the calculated band structure, electrons carriers are doped into the bands mainly composed of Bi-6px and Bi-6py components. Electron-doped BiCh2-based compounds are expected to become metallic. Indeed, superconductivity is experimentally observed in electron-doped compounds [1][2][3]. However, the real situations are not simple as expected from the band structure. Although the superconductivity in BiCh2-based compounds is emerged by carrier doping, metallic transport is sometimes absent, and weakly localized behavior (semiconducting-like behavior) is observed in electrical resistivity measurements; a good example would be optimally doped LaO0.5F0.5BiS2. In semiconducting-like samples of LaO0.5F0.5BiS2, bulk superconductivity is not observed, while weak (filamentary) superconductivity is observed. To induce bulk superconductivity in the LaO0.5F0.5BiS2 system, external pressure effects [9][10][11][12][13][14][15][16] and/or element substitution at the La site [17][18][19][20], which optimize the crystal structure, are available. Namely, both electron carrier doping and crystal structure optimization are required for the e...

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Superconductivity in Layered Chalcogenides

Mizuguchi

2014

Wiley Encyclopedia of Electrical and Electronics Engineering

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Layered chalcogenides have received much attention in the field of superconductivity because of the variety of their structures and the observation of unconventional superconductivity. Here, the crystal structure and physical properties of four novel metal chalcogenides, Fe chalcogenides, BiS 2 ‐based family, CdI 2 ‐type chalcogenides, and a possible topological superconductor Cu x Bi 2 Se 3 , are summarized. In particular, this article will focus on the correlation between the crystal structure and superconductivity of the layered chalcogenides.

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Superconductivity at 5 K in NdO0.5F0.5BiS2

Cited by 93 publications

References 17 publications

Evidence for nodeless superconductivity in NdO_1−xF_xBiS₂(x= 0.3 and 0.5) single crystals

Evidence for nodeless superconductivity in NdO_1−xF_xBiS₂(x= 0.3 and 0.5) single crystals

Intrinsic Phase Diagram of Superconductivity in the BiCh₂-Based System Without In-Plane Disorder

Superconductivity in Layered Chalcogenides

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Superconductivity at 5 K in NdO0.5F0.5BiS2

Cited by 93 publications

References 17 publications

Evidence for nodeless superconductivity in NdO1−xFxBiS2(x= 0.3 and 0.5) single crystals

Evidence for nodeless superconductivity in NdO1−xFxBiS2(x= 0.3 and 0.5) single crystals

Intrinsic Phase Diagram of Superconductivity in the BiCh2-Based System Without In-Plane Disorder

Superconductivity in Layered Chalcogenides

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Evidence for nodeless superconductivity in NdO_1−xF_xBiS₂(x= 0.3 and 0.5) single crystals

Evidence for nodeless superconductivity in NdO_1−xF_xBiS₂(x= 0.3 and 0.5) single crystals

Intrinsic Phase Diagram of Superconductivity in the BiCh₂-Based System Without In-Plane Disorder