Nematicity as a Probe of Superconducting Pairing in Iron-Based Superconductors

Fernandes, Rafael M.; Millis, Andrew J.

doi:10.1103/physrevlett.111.127001

Cited by 134 publications

(133 citation statements)

References 63 publications

(134 reference statements)

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“…However, d-wave symmetry can be also observed [60,61]. Hole doping of IBSC can lead to the transition of the gap symmetry from s ± -wave to d-wave [62][63][64]. Our main result is not affected, with similar results for other symmetries than s-wavethe FFLO is the ground state in the LTHM regime in every band.…”

Section: Numerical Results and Discussionsupporting

confidence: 74%

Multiple phase transitions in Pauli-limited iron-based superconductors

Ptok

2015

J. Phys.: Condens. Matter

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Abstract. Specific heat measurements have been successfully used to probe unconventional superconducting phases in one-band heavy-fermion and organic superconductors. We extend the method to study successive phase transitions in multi-band materials such as iron based superconductors. The signatures are multiple peaks in the specific heat, at low temperatures and high magnetic field, which can lead the experimental verification of unconventional superconducting states with non-zero total momentum.

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Section: Numerical Results and Discussionsupporting

confidence: 74%

Multiple phase transitions in Pauli-limited iron-based superconductors

Ptok

2015

J. Phys.: Condens. Matter

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“…One of the consequences of the near-degeneracy between the competing s +− and d-wave states is the suppression of the value of T c in the tetragonal phase [31,49]. The mixing between the two states promoted by orbital order, Eq.…”

Section: (B)mentioning

confidence: 99%

“…To show that these results are general and do not depend on details of the tight-binding model, we interpret them as a consequence of the mixing between the s +− and d-wave gap functions of the tetragonal state promoted by orbital order [49]:…”

Section: (B)mentioning

confidence: 99%

“…Experimentally, many optimallydoped iron-based superconductors display a large nematic susceptibility χ nem [35][36][37][38][39][40][41][42][43], implying that even a small uniaxial strain [44][45][46][47] can trigger a nematic state with sizable anisotropies in the lattice and, more interestingly, in the magnetic and orbital degrees of freedom [48]. While previous works investigated how superconductivity is affected by the nematic-induced anisotropy in the magnetic spectrum [49], little is known about the impact of the induced anisotropy in the electronic spectrum. Indeed, in the nematic state, the onsite energies of the d xz and d yz orbitals become unequal, ∆ oo = ε xz − ε yz = 0 [20,50,51], affecting the orbital content of the Fermi surface [52][53][54][55][56][57].…”

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confidence: 99%

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Manipulation of Gap Nodes by Uniaxial Strain in Iron-Based Superconductors

2014

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In the iron pnictides and chalcogenides, multiple orbitals participate in the superconducting state, enabling different gap structures to be realized in distinct materials. Here we argue that the spectral weights of these orbitals can in principle be controlled by a tetragonal symmetry-breaking uniaxial strain, due to the enhanced nematic susceptibility of many iron-based superconductors. By investigating multi-orbital microscopic models in the presence of orbital order, we show that not only Tc can be enhanced, but pairs of accidental gap nodes can be annihilated and created in the Fermi surface by an increasing external strain. We explain our results as a mixture of nearly-degenerate superconducting states promoted by strain, and show that the annihilation and creation of nodes can be detected experimentally via anisotropic penetration depth measurements. Our results provide a promising framework to externally control the superconducting properties of iron-based materials.A distinguishing feature of iron pnictides and chalcogenides [1,2] [13][14][15]. This diversity of behaviors opens up the interesting possibility of manipulating the superconducting ground state by tuning the appropriate external parameters. While this can be achieved empirically by mixing different types of doping, such as Ba(Fe 1−x Co x ) 2 (As 1−y P y ) 2 [16], control of the SC state requires understanding the mechanisms responsible for this non-universality of the gap structure.Theoretically, spin fluctuations have been widely proposed to cause pairing in iron pnictides and chalcogenides [17]. In this model, the non-universal behavior of the gap structure stems from the multi-orbital character of these materials that arises due to the 3d 6 configuration of Fe [18]. In fact, first-principle calculations [22] and ARPES experiments [19,20] reveal that the disconnected pockets that form the Fermi surface of most pnictides contain significant spectral weight from the d xz , d yz , and d xy orbitals (see Fig. 1(a) [33,34], is a distinguishing feature of the iron-based materials, since in most superconductors one SC state usually has a much lower energy than all the other ones.Therefore, in this framework, the properties of the SC state of the iron pnictides could be manipulated if the orbital content of their Fermi surface could be tuned. In this paper, we propose that this can be achieved via application of uniaxial strain ∂ i u i , where u denotes the displacement vector. Experimentally, many optimallydoped iron-based superconductors display a large nematic susceptibility χ nem [35][36][37][38][39][40][41][42][43], implying that even a small uniaxial strain [44][45][46][47] can trigger a nematic state with sizable anisotropies in the lattice and, more interestingly, in the magnetic and orbital degrees of freedom [48]. While previous works investigated how superconductivity is affected by the nematic-induced anisotropy in the magnetic spectrum [49], little is known about the impact of the induced anisotropy in the electronic spectrum. Indeed,...

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“…Recent theoretical work indicates that non-timereversal symmetry breaking s ± + d x 2 −y 2 pairing can be realized due to coupling to the nematic order parameter 62,63 . Study of this effect in the framework of the strong-coupling t−J 1 −J 2 −K model will be the subject of future work, potentially relevant to superconductivity in the thin FeSe films 64 and in the stoichiometric singlecrystalline FeSe 65 .…”

Section: 43mentioning

confidence: 99%

Competing superconducting channels in iron pnictides from the strong coupling theory with biquadratic spin interactions

Nevidomskyy

2016

J. Phys.: Condens. Matter

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We study the symmetry and strength of the superconducting pairing in a two-orbital t−J1 −J2 −K model for iron pnictides using the salve boson mean-field theory. We show that the nearest-neighbor biquadratic interaction −K( Si · Sj ) 2 inflences the superconducting pairing phase diagram by promoting the d x 2 −y 2 B1g and the s x 2 +y 2 A1g channels. The resulting phase diagram consists of several competing pairing channels, including an isotropic s± A1g channel, an anisotropic d x 2 −y 2 B1g channel, and two s + id pairing channels. We have investigated the evolution of superconducting states with electron doping, and find that with the biquadratic interaction various pairing channels may dominate at different doping concentrations. We show that this is crucial in understanding the doping evolution of superconducting gap anisotropy observed in some angle resolved photoemission spectrum measurements.

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Nematicity as a Probe of Superconducting Pairing in Iron-Based Superconductors

Cited by 134 publications

References 63 publications

Multiple phase transitions in Pauli-limited iron-based superconductors

Multiple phase transitions in Pauli-limited iron-based superconductors

Manipulation of Gap Nodes by Uniaxial Strain in Iron-Based Superconductors

Competing superconducting channels in iron pnictides from the strong coupling theory with biquadratic spin interactions

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