Effect of weak disorder on the phase competition in iron pnictides

Hoyer, Mareike; Syzranov, Sergey; Schmalian, Joerg

doi:10.1103/physrevb.89.214504

Cited by 16 publications

(22 citation statements)

References 44 publications

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“…The two orders coexist when β 1 β 2 > (γ 1 − |γ 2 |) 2 . This condition can be satisfied in the presence of disorder 54,55 . The relative phase θ between ∆ 1 = |∆ 1 |e iψ+θ/2 and ∆ 2 = |∆ 2 |e iψ−θ/2 is determined by the sign of the γ 2 term in (13).…”

Section: Introductionmentioning

confidence: 99%

Time-Reversal Symmetry Breaking Superconductivity in the Coexistence Phase with Magnetism in Fe Pnictides

2014

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We argue that superconductivity in the coexistence region with spin-density-wave (SDW) order in weakly doped Fe-pnictides differs qualitatively from the ordinary s +− state outside the coexistence region, as it develops an additional gap component which is a mixture of intra-pocket singlet (s ++ ) and inter-pocket spin-triplet pairings (the t−state). The coupling constant for the t−channel is proportional to the SDW order and involves interactions that do not contribute to superconductivity outside of the SDW region. We argue that the s +− and t−type superconducting orders coexist at low temperatures, and the relative phase between the two is in general different than 0 or π, manifesting explicitly the breaking of the time-reversal symmetry promoted by long-range SDW order. We show that this exotic state emerges already in the simplest model of Fe-pnictides, with one hole pocket and two symmetry-related electron pockets. We argue that in some parameter range time-reversal gets broken even before long-range superconducting order develops. IntroductionIron-based superconductors (FeSCs) have been the subject of intense study since 20081 . Their rich phase diagram includes the regions of superconductivity (SC), spin density wave (SDW), nematic order, and a region where SDW, SC, and nematic order coexist 2 . Outside the SDW/nematic region, SC develops in the spin-singlet channel and in most of Fe-based superconductors has s−wave symmetry with a π phase shift between the SC order parameters on hole and on electron pockets ( s +− gap structure) 3,4 . It has been recently argued by several groups that the multiband structure of FeSCs allows for superconducting states with more exotic properties 5-11,14-21 . Of particular interest are SC states that break time-reversal symmetry (TRS), as such states have a plethora of interesting properties like, e.g., novel collective modes 12,13,15,20 . TRS-broken states emerge when the phase differences ψ i between SC order parameters on different Fermi surfaces (FS) are not multiples of π.The two current proposals for TRS breaking in FeSCs are s + id 5,[9][10][11]19 and s + is states 6,15,20,21 . The first emerges when attractions in the d−wave and s−wave channels are of near-equal strength. The second emerges when there is a competition between different s +− states favored by inter-pocket and intra-pocket interactions. Both of these proposals were, however, argued to be applicable only to strongly hole or electron-doped FeSCc. For weakly/moderately doped FeSCs the common belief is that s +− superconductivity is robust. In this communication we argue that an exotic state which breaks TRS can emerge already at low doping, in a range where SC is known [22][23][24][25][26][27][28][29][30] to emerge from a pre-existing SDW state. Previous works on SC in the coexistence region focused on the SDW-induced modification of the form of s +− gap 31-37 . We argue that there is another effect -SDW order also induces attraction in another pairing channel, for which the order parameter is an admix...

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Section: Introductionmentioning

confidence: 99%

Time-Reversal Symmetry Breaking Superconductivity in the Coexistence Phase with Magnetism in Fe Pnictides

2014

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“…The effects of disorder on the phase diagram, including pair-breaking scattering, and on the penetration depth were investigated in Refs. [38][39][40][41][42][43][44][45]. We study the effect of disorder on λ L in a systematic way and analyze its behavior in the part of the phase diagram where the SC and SDW phases coexist.…”

Section: 7mentioning

confidence: 99%

“…In the context of iron-based superconductors, the quasiclassical approximation works well since both superconducting and magnetic correlation lengths greatly exceed λ F . 42,43,45,46 The central object in the quasiclassical approach is the Eilenberger function…”

Section: B Quasiclassical Approximationmentioning

confidence: 99%

Magnetic penetration depth in disordered iron-based superconductors

Dzero¹,

Khodas²,

Klironomos³

et al. 2015

Phys. Rev. B

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We study the effect of disorder on the London penetration depth in iron-based superconductors. The theory is based on a two-band model with quasi-two-dimensional Fermi surfaces, which allows for the coexistence region in the phase diagram between magnetic and superconducting states in the presence of intraband and interband scattering. Within the quasiclassical approximation we derive and solve Eilenberger's equations, which include a weak external magnetic field, and provide analytical expressions for the penetration depth in the various limiting cases. A complete numerical analysis of the doping and temperature dependence of the London penetration depth reveals the crucial effect of disorder scattering, which is especially pronounced in the coexistence phase. The experimental implications of our results are discussed.

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“…and hence the density wave is stable against impurities satisfying the criterion (23). The proof is presented in Appendix A.…”

Section: Symmetry Protection Of Density Wavesmentioning

confidence: 99%

Pair breaking due to orbital magnetism in iron-based superconductors

et al. 2015

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We consider superconductivity in the presence of impurities in a two-band model suited for the description of iron-based superconductors. We analyze the effect of interband scattering processes on superconductivity, allowing for orbital, i. e., non-spin-magnetic but time-reversal-symmetry-breaking impurities. Pair-breaking in such systems is described by a nontrivial phase in an interbandscattering matrix element. We find that the transition temperature of conventional superconductors can be suppressed due to interband scattering, whereas unconventional superconductors may be unaffected. We also discuss the stability of density wave phases in the presence of impurities. As an example, we consider impurities associated with imaginary charge density waves that are of interest for iron-based superconductors.

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Effect of weak disorder on the phase competition in iron pnictides

Cited by 16 publications

References 44 publications

Time-Reversal Symmetry Breaking Superconductivity in the Coexistence Phase with Magnetism in Fe Pnictides

Time-Reversal Symmetry Breaking Superconductivity in the Coexistence Phase with Magnetism in Fe Pnictides

Magnetic penetration depth in disordered iron-based superconductors

Pair breaking due to orbital magnetism in iron-based superconductors

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