Vertical Line Nodes in the Superconducting Gap Structure of 
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We compute and compare even-and odd-parity superconducting order parameters of strontium ruthenate (Sr2RuO4) in the limit of weak interactions, resulting from a fully microscopic threedimensional model including spin-orbit coupling. We find that odd-parity helical and even-parity dwave order are favored for smaller and larger values of the Hund's coupling parameter J, respectively. Both orders are found compatible with specific heat data and the recently-reported nuclear magnetic resonance (NMR) Knight shift drop [A. Pustogow et al. arXiv:1904.00047 (2019]. The chiral p-wave order, numerically very competitive with helical order, sharply conflicts with the NMR experiment.

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“…4 (a). The character of the minima also appear likely to agree with thermal Hall measurements 15,16 .…”

supporting

confidence: 72%

Superconducting order of Sr2RuO4 from a three-dimensional microscopic model

Røising¹,

Scaffidi

Flicker³

et al. 2019

Phys. Rev. Research

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“…However, nodal surfaces would lead to a finite density of states at the Fermi level within the superconducting state, which seems excluded [13]. Simple single-orbital pairing functions involving onlyâ z , or a combination ofâ x and a y , would lead to nodal surfaces coinciding with the Fermi surfaces of the bands not involved in pairing.…”

Section: Nodes and The Density Of Statesmentioning

confidence: 99%

Group-theoretical classification of superconducting states of strontium ruthenate

Kaba

Sénéchal

2019

Phys. Rev. B

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The possible superconducting states of strontium ruthenate (Sr 2 RuO 4 ) are organized into irreducible representations of the point group D 4h , with a special emphasis on nodes occurring within the superconducting gap. Our analysis covers the cases with and without spin-orbit coupling and takes into account the possibility of inter-orbital pairing within a three-band, tight-binding description of Sr 2 RuO 4 . No dynamical treatment if performed: we are confining ourselves to a group-theoretical analysis. The case of uniaxial deformations, under which the point group symmetry is reduced to D 2h , is also covered. It turns out that nodal lines, in particular equatorial nodal lines, occur in most representations. We also highlight some results specific to multiorbital superconductivity. Among other things, we find that odd inter-orbital pairing allows to combine singlet and triplet superconductivity whithin the same irreducible representation, that pure inter-orbital superconductivity leads to nodal surfaces and that the notion of nodes imposed by symmetry is not clearly defined. arXiv:1905.10467v1 [cond-mat.supr-con] 24 May 2019 H 0 = t 1 〈r,r 〉,σ c † r,3,σ c r ,3,σ + t 2 〈r,r 〉 2 ,σ c † r,3,σ c r ,3,σ + t 3   〈r,r 〉 x ,σ c † r,1,σ c r ,1,σ + 〈r,r 〉 y ,σ c † r,2,σ c r ,2,σ   + λ 〈r,r 〉 2 ,σ c † r,1,σ c r ,2,σ + H.c. + i κ 2 r l,m,n lmn c † r,l,σ c r,m,σ τ n σσ + e r,σ,m=1,2 c † r,m,σ c r,m,σ − µ r,m,σ c † r,m,σ c r,m,σ (1)where c r,m,σ is the annihilation operator for orbital m = 1, 2, 3 of spin projection σ at site r; 〈r, r 〉 stands for nearestneighbor pairs and 〈r, r 〉 2 for second (diagonal) neighbors; 〈r, r 〉 x stands for nearest-neighbor pairs in the x direction, and likewise for the y direction. The κ term is a spin-orbit coupling, where τ 1,2,3 are the Pauli matrices and lmn the Levi-Civita antisymmetric symbol. Note that the chosen labeling of the three orbitals (d yz → 1, d xz → 2, d x y → 3) is important in this expression. Fig. 1 illustrates the orbitals and hopping terms involved (t 1,2,3 and λ). On that figure, the three orbitals have been separated vertically for clarity. The first two orbitals (1 and 2) are separated by an energy e from the third. The interaction terms include local Coulomb interactions U (intra-orbital) and U (inter-orbital), as well as Hund couplings J and J : H 1 = r    U l n r,l,↑ n r,l,↓ + m =m   U σ,σ n r,m,σ n r,m ,σ + J 2 σ,σ c † r,m,σ c † r,m ,σ c r,m,σ c r,m ,σ + J 2 σ =σ c † r,m,σ c † r,m,σ c r,m ,σ c r,m ,σ

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“…Hassinger et al [560] measured the thermal conductivity of a single crystal of Sr2RuO4 (Tc=1.2 K, residual resistivity 0=0.24 -cm) in fields down to Hc2/100 and temperatures down to Tc/30 both in-plane and along the c-axis. Their analysis indicates vertical line nodes on all three sheets of the Fermi surface in Sr2RuO4.…”

Section: C(h)/(h)mentioning

confidence: 99%

Unconventional superconductivity

Stewart

2017

Advances in Physics

198

163

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Abstract:"Conventional" superconductivity, as used in this review, refers to electron-phonon coupled superconducting electron pairs described by BCS theory. Unconventional superconductivity refers to superconductors where the Cooper pairs are not bound together by phonon-exchange but instead by exchange of some other kind, e. g. spin fluctuations in a superconductor with magnetic order either coexistent or nearby in the phase diagram. Such unconventional superconductivity has been known experimentally since heavy fermion CeCu2Si2, with its strongly correlated 4f electrons, was discovered to superconduct below 0.6 K in 1979. Since the discovery of unconventional superconductivity in the layered cuprates in 1986, the study of these materials saw Tc jump to 164 K by 1994. Further progess in high temperature superconductivity would be aided by understanding the cause of such unconventional pairing. This review compares the fundamental properties of 9 unconventional superconducting classes of materialsfrom 4f-electron heavy fermions to organic superconductors to classes where only three known members exist to the cuprates with over 200 examples -with the hope that common features will emerge to help theory explain (and predict!) these phenomena. In addition, three new emerging classes of superconductors (topological, interfacial -e. g. FeSe on SrTiO3, and H2S under high pressure) are briefly covered, even though their "conventionality" is not yet fully determined.

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Vertical Line Nodes in the Superconducting Gap Structure of Sr2RuO4

Cited by 140 publications

References 65 publications

Superconducting order of Sr2RuO4 from a three-dimensional microscopic model

Superconducting order of Sr2RuO4 from a three-dimensional microscopic model

Group-theoretical classification of superconducting states of strontium ruthenate

Unconventional superconductivity

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