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Kretzschmar, Florian; Muschler, B.; Böhm, Thomas; Baum, Andreas; Hackl, R.; Wen, Hao; Tsurkan, V.; Deisenhofer, J.; Loidl, A.

doi:10.1103/physrevlett.110.187002

Cited by 60 publications

(126 citation statements)

References 34 publications

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“…Recently, we have shown unambiguous evidence for the appearance of SC nodes in optimally-doped Ba 1−x Rb x Fe 2 As 2 upon applied pressure, consistent with a change from a nodeless s +− -wave state to a d-wave state 39 . Interestingly, the theoretical calculations [41][42][43][44][45][46][47] as well as Raman experiments 48,49 revealed a sub-dominant d-wave state close in energy to the dominant s +− state. It seems that pressure affects this intricate balance, and tip the balance in favor of the d-wave state.…”

Section: Introductionmentioning

confidence: 99%

Probing the pairing symmetry in the over-doped Fe-based superconductorBa0.35Rb0.65Fe2As2as a function of hydrostatic pressure

et al. 2016

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Probing the pairing symmetry in the over-doped Fe- We report muon spin rotation experiments on the magnetic penetration depth λ and the temperature dependence of λ −2 in the over-doped Fe-based high-temperature superconductor (Fe-HTS) Ba1−xRbxFe2As2 (x = 0.65) studied at ambient and under hydrostatic pressures up to p = 2.3 GPa. We find that in this system λ −2 (T ) is best described by d-wave scenario. This is in contrast to the case of the optimally doped x = 0.35 system which is known to be a nodeless s +− -wave superconductor. This suggests that the doping induces the change of the pairing symmetry from s +− to d-wave in Ba1−xRbxFe2As2. In addition, we find that the d-wave order parameter is robust against pressure, suggesting that d is the common and dominant pairing symmetry in over-doped Ba1−xRbxFe2As2. Application of pressure of p = 2.3 GPa causes a decrease of λ(0) by less than 5 %, while at optimal doping x = 0.35 a significant decrease of λ(0) was reported. The superconducting transition temperature Tc as well as the gap to Tc ratio 2∆/kBTc show only a modest decrease with pressure. By combining the present data with those previously obtained for optimally doped system x = 0.35 and for the end member x = 1 we conclude that the SC gap symmetry as well as the pressure effects on the SC quantities strongly depend on the Rb doping level. These results are discussed in the light of the putative Lifshitz transition, i.e., a disappearance of the electron pockets in the Fermi surface of Ba1−xRbxFe2As2 upon hole doping.

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Section: Introductionmentioning

confidence: 99%

Probing the pairing symmetry in the over-doped Fe-based superconductorBa0.35Rb0.65Fe2As2as a function of hydrostatic pressure

et al. 2016

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“…It has been well characterized that both cuprates and conventional phonon-mediated superconductors are characterized by distinct d-wave and s-wave pairing symmetries with nodal and nodeless gap distributions, respectively. There is no general consensus on the nature of pairing in iron-based superconductors leaving the perspectives * xjchen@hpstar.ac.cn ranging from S ++ wave, to S ± , and to d wave [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. In addition, from 59 Co and 75 As nuclear magnetic resonance measurements, the spin-triplet order parameter was ruled out in BaFe 1.8 Co 0.2 As 2 [25].…”

Section: Introductionmentioning

confidence: 99%

Nodeless superconductivity in the presence of spin-density wave in pnictide superconductors: The case ofBaFe2−xNixAs2

Abdel-Hafiez

Zhang

et al. 2015

Phys. Rev. B

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The characteristics of Fe-based superconductors are manifested in their electronic, magnetic properties, and pairing symmetry of the Cooper pair, but the latter remain to be explored. Usually in these materials, superconductivity coexists and competes with magnetic order, giving unconventional pairing mechanisms. We report on the results of the bulk magnetization measurements in the superconducting state and the low-temperature specific heat down to 0.4 K for BaFe 2−x Ni x As 2 single crystals. The electronic specific heat displays a pronounced anomaly at the superconducting transition temperature and a small residual part at low temperatures in the superconducting state. The normal-state Sommerfeld coefficient increases with Ni doping for x = 0.092, 0.096, and 0.10, which illustrates the competition between magnetism and superconductivity. Our analysis of the temperature dependence of the superconducting-state specific heat and the London penetration depth provides strong evidence for a two-band s-wave order parameter. Further, the data of the London penetration depth calculated from the lower critical field follow an exponential temperature dependence, characteristic of a fully gapped superconductor. These observations clearly show that the superconducting gap in the nearly optimally doped compounds is nodeless.

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“…In contrast, since orbital fluctuations reside in the B 1g charge channel a resonance mode develops due to the orbital fluctuations which can certainly be detected by the Raman spectroscopy. Such a resonance mode can, in principle, arise from a sub-dominant d-wave pairing channel [19,21,22]. Our key point here is that d-wave sub-dominant pairing and ferro-orbital order both have the same space group symmetry of the Raman B 1g mode.…”

mentioning

confidence: 96%

“…Indeed, a magnetic resonance mode at wavevector (π, 0) has been observed in the pnictides and has been attributed to spin fluctuations [1]. However, recent Raman scattering measurements [19], a zero wave-vector probe, have observed a superconductivity-induced peak in the B 1g channel. Since this peak is sharp and occurs at zero wavevector, for two reasons, it is not likely that it is due to to spin fluctuations.…”

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confidence: 99%

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Orbital resonance mode in superconducting iron pnictides

Lee

Phillips

2013

EPL

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-We show that the fluctuations associated with ferro orbital order in the dxz and dyz orbitals can develop a sharp resonance mode in the superconducting state with a nodeless gap on the Fermi surface. This orbital resonance mode appears below the particle-hole continuum and is analogous to the magnetic resonance mode found in various unconventional superconductors. If the pairing symmetry is s±, a dynamical coupling between the orbital ordering and the d-wave subdominant pairing channels is present by symmetry. Therefore the nature of the resonance mode depends on the relative strengths of the fluctuations in these two channels, which could vary significantly for different families of the iron based superconductors. The application of our theory to a recent observation of a new δ-function-like peak in the B1g Raman spectrum of Ba0.6K0.4Fe2As2 is discussed, and we predict that the same orbital resonance mode can be detected in electron-energy-loss-spectroscopy (EELS).Introduction. -For high-temperature superconductors, cuprates and iron pnictides, resolving the nature of the fluctuations in both the normal and superconducting states remains a crucial question as it holds the key to the pairing mechanism. In cuprates, due to the strong antiferromagnetism in the parent compounds, it is widelybelieved that the antiferromagnetic spin fluctuations are the most important ingredient in the pairing mechanism. One of the marquee indicators of this is the magnetic resonance mode [1] observed in the superconducting state of every cuprate. From the BCS theory, the spin-flip susceptibility of an electron scattered from k to k + q in the superconducting state gains an extra coherence factor which is proportional to (1 − sgn(∆( k))sgn(∆( k + q))). Since the gap symmetry of the cuprates is d-wave signified by sgn(∆( k)) = −sgn(∆( k + Q)), the spin excitations near q = Q are compatible with superconductivity. It can be further shown [2-6] that a sharp δ-function-like resonance mode in the spin-flip susceptibility requires an antiferromagnetic spin interaction to pull the resonance mode to an energy below the particle-hole continuum. In other words, despite some dependence on the detailed electronic structure, the existence of the magnetic resonance mode is predominantly determined by the gap symmetry and the nature of the spin interaction. As a result, it has been identified as an unambiguous [1] indicator that antiferromagnetic spin fluctuations remain strong in the super-

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Raman-Scattering Detection of Nearly Degenerates-Wave andd-Wave Pairing Channels in Iron-BasedBa0.6K0.4

Cited by 60 publications

References 34 publications

Probing the pairing symmetry in the over-doped Fe-based superconductorBa0.35Rb0.65Fe2As2as a function of hydrostatic pressure

Probing the pairing symmetry in the over-doped Fe-based superconductorBa0.35Rb0.65Fe2As2as a function of hydrostatic pressure

Nodeless superconductivity in the presence of spin-density wave in pnictide superconductors: The case ofBaFe2−xNixAs2

Orbital resonance mode in superconducting iron pnictides

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