Probing the pairing symmetry in the over-doped Fe-based superconductor<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Ba</mml:mi><mml:mrow><mml:mn>0.35</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mi>Rb</mml:mi><mml:mrow><mml:mn>0.65</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mi>Fe</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>As</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>as a function of hydrostatic pressure

Guguchia, Zurab; Khasanov, R.; Bukowski, Z.; Rohr, Fabian von; Medarde, M.; Biswas⃰, Pabitra Kumar; Luetkens, H.; Amato, A.; Morenzoni, E.

doi:10.1103/physrevb.93.094513

Cited by 15 publications

(32 citation statements)

References 73 publications

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“…For single crystals, f L varies between zero and unity as the orientation between field and polarization changes from being parallel to perpendicular. In addition to the magnetically ordered contribution, there is a PM signal component characterized by the densely distributed network of nuclear dipolar moments σ and dilute electronic moments with random orientations λ [28]. The temperature-dependent magnetic ordering fraction 0 ≤ F ≤ 1 governs the trade-off between magneticallyordered and PM behaviors.…”

Section: A Zero Field µSr Resultsmentioning

confidence: 99%

“…The defining parameters in (2) are the precession frequency ν, the relaxation rates σ SC and σ nm characterizing the damping due to the formation of FLL in the SC state and the nuclear magnetic dipolar contribution, respectively, and an exponential relaxation rate for fieldinduced magnetism λ Mag [91]. The model in (2) has been previously used [28,92] for Fe-HTS in the presence of dilute or fast fluctuating electronic moments and it was demonstrated to be sufficiently precise for extracting the SC depolarization rate as a function of temperature.…”

Section: A Tf-µsr Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Disentangling superconducting and magnetic orders in NaFe1−xNixAs using muon spin rotation

Cheung¹,

Guguchia²,

Frandsen³

et al. 2018

Phys. Rev. B

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antiferromagnetic (AFM) order [1][2][3]. One of the grand challenges in understanding the behavior of these systems is determining the physical mechanism responsible for superconductivity. Essential information on the nature of superconductivity in strongly correlated electron systems can be deduced by investigating their phase diagrams as well as the superconducting (SC) gap structure.In the parent compound of many Fe-HTS, a spin density wave forms with spins ordered antiparallel to each arXiv:1802.04458v1 [cond-mat.supr-con]

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Section: A Zero Field µSr Resultsmentioning

confidence: 99%

Section: A Tf-µsr Resultsmentioning

confidence: 99%

Disentangling superconducting and magnetic orders in NaFe1−xNixAs using muon spin rotation

Cheung¹,

Guguchia²,

Frandsen³

et al. 2018

Phys. Rev. B

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show abstract

“…Note that for an electronic or magnetic pairing mechanism, some of the electrons are components of the pairing interaction, and therefore one expects

n_{s} / n < 1

. Using the experimental London penetration depth data of

Λ^{BaRb} = 257

Λ^{BaRb} = 194

nm ,

λ^{CaNa} = 0.89

, and adopting a comparable total coupling constant

λ^{BaRb} \approx 1

and similar unscreened plasma frequencies, we estimate

n_{s}^{normalBaRb} \approx 0.6

, only. This way by quenching the weakly coupled

d_{xy}

‐derived band by the combined effect of a weak magnetic field and disorder, the single ‐gap d ‐wave scenario might be in principle understood.…”

Section: Introductionmentioning

confidence: 86%

“…If one wishes to do a similar study in the superconducting state, then some additional care must be taken to account for the possibility that not all electrons take part in forming the superconducting condensate. For example, a crude rescaling of the zero temperature London penetration depth

Λ

for hole ‐overdoped system

{Ba}_{0.35} {Rb}_{0.65}

Fe 2 As 2 , which is a candidate for d ‐wave superconductor as in Rb‐122, gives

\frac{Ω_{p}^{BaRb}}{Ω_{p}^{CaNa}} \frac{Λ^{BaRb} false(0 false)}{Λ^{CaNa} false(0 false)} \approx \sqrt{\frac{false(1 + λ^{BaRb} false) n^{BaRb} n_{s}^{CaNa}}{n_{s}^{BaRb} n^{CaNa} false(1 + λ^{CaNa} false)}},

where n is the total charge density of all conduction electrons, and

n_{s}

is the part residing in the condensate at

T = 0

. Note that for an electronic or magnetic pairing mechanism, some of the electrons are components of the pairing interaction, and therefore one expects

n_{s} / n < 1

.…”

Section: Introductionmentioning

confidence: 99%

Constraints on the total coupling strengthto bosons in the iron based superconductors

Drechsler

Johnston

Grinenko

et al. 2017

Phys. Status Solidi B

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Despite the fact that the Fe-based superconductors (FeSCs) were discovered nearly ten years ago, the community is still devoting a tremendous effort towards elucidating their relevant microscopic pairing mechanism(s) and interactions. At present, there is still no consistent interpretation of their normal state properties, where the strength of the electron-electron interaction and the role of correlation effects are under debate. Here, we examine several common materials and illustrate various problems and concepts that are generic for all FeSCs. Based on empirical observations and qualitative insight from density functional theory, we show that the superconducting and low-energy thermodynamic properties of the FeSCs can be described semi-quantitively within multiband Eliashberg theory. We account for an important high-energy mass renormalization phenomenologically, and in agreement with constraints provided by thermodynamic, optical, and angle-resolved photoemission data. When seen in this way, all FeSCs with T c < 40 K studied so far are found to belong to an intermediate coupling regime. This finding is in contrast to the strong coupling scenarios proposed in the early period of the FeSC history. We also discuss several related issues, including the role of band shifts as measured by the positions of van Hove singularities, and the nature of a recently suggested quantum critical point in the strongly hole-doped systems AFe 2 As 2 (A = K, Rb, Cs). Using high-precision full relativistic GGA-band structure calculations, we arrive at a somewhat milder mass renormalization in comparison with previous studies. From the calculated mass anisotropies of all Fermi surface sheets, only the ε-pocket near the corner of the BZ is compatible with the experimentally observed anisotropy of the upper critical field, pointing to its dominant role in the superconductivity of these three compounds.

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“…Following these criteria, one may immediately conclude that s + id pairing favors the second-order phase while neither s + d nor s + is pairing do. The mixed-pairing state we consider above has been extensively studied in iron pnictides, particularly 122 compounds [60][61][62][63][64][65][66] like Ba 1−x K x Fe 2 As 2 . In these materials, the pairing symmetry is expected to change from a nodeless s ± form around optimal doping (x ∼ 0.4) [67] to a form with nodal gaps in the heavily hole-doped region, for instance, KFe 2 As 2 (x = 1).…”

mentioning

confidence: 99%

Second-Order Topological Superconductors with Mixed Pairing

Zhu

2019

Phys. Rev. Lett.

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We show that a two-dimensional semiconductor with Rashba spin-orbit coupling could be driven into the second-order topological superconducting phase when a mixed-pairing state is introduced. The superconducting order we consider involves only even-parity components and meanwhile breaks time-reversal symmetry. As a result, each corner of a square-shaped Rashba semiconductor would host one single Majorana zero mode in the second-order nontrivial phase. Starting from edge physics, we are able to determine the phase boundaries accurately. A simple criterion for the secondorder phase is further established, which concerns the relative position between Fermi surfaces and nodal points of the superconducting order parameter. In the end, we propose two setups that may bring this mixed-pairing state into the Rashba semiconductor, followed by a brief discussion on the experimental feasibility of the two platforms.Topological superconductors (TSCs) distinguish themselves from trivial ones in the robust midgap states-Majorana zero modes (MZMs)-that could form either at local defects or boundaries [1-9]. Among the various proposals for TSCs, semiconducting systems with Rashba spin-orbit coupling (RSOC) [10-13] as well as topological insulating systems [14] have attracted the most attention. In both platforms, signatures of MZMs have been observed when conventional s-wave pairing is introduced through proximity effect [15][16][17][18][19][20][21][22][23][24][25].In these conventional, also termed as first-order, TSCs, topologically nontrivial bulk in d dimensions is usually accompanied by MZMs confined at (d − 1)-dimensional boundaries, the so-called bulk-boundary correspondence. Very recently, this correspondence was extended in topological phases of nth order [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45], where topologically protected gapless modes emerge at (d − n)-dimensional boundaries. In Refs. [46][47][48][49], the authors demonstrate that a topological insulator could be transformed into a second-order TSC when unconventional pairing with the s ± -or d x 2 −y 2 -wave form is introduced. Looking back at the history of first-order TSCs, one may then ask if it is possible for a Rashba semiconductor (RS), which is itself a trivial system as opposed to topological insulators, to accommodate such a higher-order nontrivial phase as well. In this work, we will show that it is possible, provided a mixed-pairing state that exhibits both extended s-wave and d x 2 −y 2 -wave symmetries could be induced therein.Admixture of the two aforementioned pairing states was envisioned shortly after the discovery of iron-based superconductors (FeSCs) [50][51][52][53]. Since then tremendous efforts have been made to identify this mixed-pairing order [54,55]. In this Letter, we shall consider a general mixed state that could reduce to three intensively studied mixed pairings in FeSCs, that is, s + d [56], s + is [57] and s + id [50,52]. Our main finding is that, such a pairing state alone could possibly drive ...

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

Cited by 15 publications

References 73 publications

Disentangling superconducting and magnetic orders in NaFe1−xNixAs using muon spin rotation

Disentangling superconducting and magnetic orders in NaFe1−xNixAs using muon spin rotation

Constraints on the total coupling strengthto bosons in the iron based superconductors

Second-Order Topological Superconductors with Mixed Pairing

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