Spin Density Wave Fluctuations and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>p</mml:mi></mml:math>-Wave Pairing in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>Sr</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>RuO</mml:mi><mml:mn>4</mml:mn></mml:msub></mml:math>

Huo, Jia-Wei; Rice, T. M.; Zhang, Fuchun

doi:10.1103/physrevlett.110.167003

Cited by 41 publications

(40 citation statements)

References 29 publications

(44 reference statements)

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“…These calculations were extended by Scaffidi et al [30] to include interband and spin-orbit coupling yielding similar sized gaps on all bands without tuning of parameters. In contrast the recent analysis by Huo, Rice and Zhang argues in favor of superconductivity arising in the Q2D bands with the nesting fluctuations perturbing the superconductivity [31]. Experimentally, the observation of a strong enhancement of the superconducting T c (by a factor 2!)…”

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confidence: 78%

“…the pairing [31]. If superconductivity directly arises from the Q1D bands as active bands, which thus exhibit a large gap, there must be a clear impact on the associated incommensurate magnetic excitations.…”

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confidence: 99%

“…If superconductivity directly arises from the Q1D bands as active bands, which thus exhibit a large gap, there must be a clear impact on the associated incommensurate magnetic excitations. Several calculations explicitly predict the occurrence of a resonance mode in at least one of the spin excitation channels for p wave superconducting symmetry [31,[37][38][39]. On the other hand, if superconductivity is mainly driven by the Q2D band associated with ferromagnetic fluctuations, a lower gap in the Q1D bands and only a small impact on the magnetic fluctuations is expected [16,31].…”

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Absence of a Large Superconductivity-Induced Gap in Magnetic Fluctuations of Sr2RuO4

et al. 2017

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Inelastic neutron scattering experiments on Sr2RuO4 determine the spectral weight of the nesting induced magnetic fluctuations across the superconducting transition. There is no observable change at the superconducting transition down to an energy of ∼0.35 meV, which is well below the 2∆ values reported in several tunneling experiments. At this and higher energies magnetic fluctuations clearly persist in the superconducting state. Only at energies below ∼0.3 meV evidence for partial suppression of spectral weight in the superconducting state can be observed. This strongly suggests that the one-dimensional bands with the associated nesting fluctuations do not form the active, highly gapped bands in the superconducting pairing in Sr2RuO4.Sr 2 RuO 4 is one of the best studied unconventional superconductors [1-5] but its pairing symmetry and mechanism still remain a subject of very active debate. There is newly added evidence in favor of the most advocated symmetry of the superconducting order, namely the spintriplet chiral p-wave symmetry, such as the increase in the Knight shift expected in the equal-spin-pairing (ESP) triplet state [6], observation of the surface density of states consistent with the chiral edge state [7], and the magnetization steps corresponding to the half-quantum fluxoids [8]. On the other hand, there are results challenging the p-wave pairing scenario, such as the strong limiting of the in-plane upper critical fields [9], the firstorder superconducting transition [10,11], and the absence of the chiral edge current [12]. At present, there seems no symmetry model which can explain all the experimental facts available. If the most advocated symmetry of the superconducting order is correct, Sr 2 RuO 4 would be a topological superconductor proposed as a promising candidate for quantum computing [13,14].Another prominent feature of Sr 2 RuO 4 is that its normal state is quantitatively well characterized as a quasitwo-dimensional (Q2D) Fermi liquid [2,3]. The Fermi surface consists of three cylindrical sheets [2]: two originate from the d xz and d yz orbitals, called the α and β bands, and retain a quasi-one-dimensional (Q1D) character as well; the other one from the d xy , called the γ band, shows a Q2D character. All three bands disperse weakly along the interlayer c direction [15]. In such a multiband system with distinct orbital symmetries, superconductivity may be strongly orbital dependent [16]. The strong nesting between the Q1D bands results in strongly enhanced spin-density wave (SDW) fluctuations [17][18][19][20][21][22] and even minor chemical substitution leads to static ordering of this SDW instability with the moment along the c direction. Only 2.5% of Ti induce this SDW phase [23,24], and recent muSR experiments and neutron scattering studies show that the same magnetic order occurs upon replacing Sr with isovalent Ca [25,26]. Such spin fluctuations originating from the nesting of the Q1D Fermi surface sheets cannot easily lead to the most likely chiral superconducting state [2]. The...

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Absence of a Large Superconductivity-Induced Gap in Magnetic Fluctuations of Sr2RuO4

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“…Although still under debate [33][34][35], the cylindrical γ band is widely considered to be the primary source of p-wave pairing [3,36]. The small c-axis dispersion in this nearly cylindrical γ Fermi surface can be incorporated by treating it as an elongated uniaxial ellipsoid, characterized by the effective mass anisotropy of the quasi-particles m c ≫ m a = m b = m ab .…”

Section: Modelmentioning

confidence: 99%

Is the anisotropy of the upper critical field of Sr₂RuO₄consistent with a helicalp-wave state?

Zhang¹,

Lörscher²,

Gu³

et al. 2014

J. Phys.: Condens. Matter

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“…Previous theories treat either the two-dimensional (2D) γ-band derived from the xy orbital, [18][19][20][21] or the quasione-dimensional (1D) α and β bands derived from the xz and yz orbitals. [16,22] However, the evolution of wavevectors of the spin fluctuations is beyond such models, and in fact can only be accounted for by a complete three-band model. This in turn dictates the properties of the SC state mentioned above.…”

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Theory of superconductivity in a three-orbital model of Sr ₂ RuO ₄

Wang¹,

Platt²,

Yang³

et al. 2013

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In conventional and high transition temperature copper oxide and iron pnictide superconductors, the Cooper pairs all have even parity. As a rare exception, Sr2RuO4 is the first prime candidate for topological chiral p-wave superconductivity, which has time-reversal breaking odd-parity Cooper pairs known to exist before only in the neutral superfluid 3 He. However, there are several key unresolved issues hampering the microscopic description of the unconventional superconductivity. Spin fluctuations at both large and small wavevectors are present in experiments, but how they arise and drive superconductivity is not yet clear. Spontaneous edge current is expected but not observed conclusively. Specific experiments point to highly band-and/or momentum-dependent energy gaps for quasiparticle excitations in the superconducting state. Here, by comprehensive functional renormalization group calculations with all relevant bands, we disentangle the various competing possibilities. In particular we show the small wavevector spin fluctuations, driven by a single two-dimensional band, trigger p-wave superconductivity with quasi-nodal energy gaps.PACS numbers: 74.20.Rp, 71.27.+a Very soon after the discovery of superconductivity in Sr 2 RuO 4 [1], it was proposed that the superconducting (SC) pairing is of unconventional nature [2,3]. Later experiments have provided evidence that the Cooper pair in the SC state is of odd parity [4] with total spin equal to one [5]. Further evidence indicates the superconductivity to be chiral, breaking time reversal symmetry [6,7]. Sr 2 RuO 4 is thus the first prime candidate for a chiral p-wave superconductor [8][9][10][11], an interesting analogue of the neutral superfluid 3 He. It has recently received great interest as by suitable manipulations it may support zero energy Majorana bound states in vortices [12], the building block for topological quantum computing [13]. However, there are a number of outstanding issues associated with the chiral p-wave superconductivity in Sr 2 RuO 4 . First, p-wave spin triplet pairing is expected to be associated with spin fluctuations at small wavevector. However, the spin density wave (SDW) fluctuation observed in Sr 2 RuO 4 is dominated by a large wavevector at higher temperatures and coexist with a feature at small wavevector at lower temperatures. [14] A resolution of this puzzle is vital to understand the superconductivity. Second, one would expect a spontaneous electric current at the edge of the RuO 2 layers as a result of the chiral SC state. The edge current, however, has not been observed conclusively in experiments.[15] One possible reason is the edge current is very fragile and difficult to establish against disorders. Another possibility is a topological cancellation from hole-like and electron-like bands, [16] posing a question as whether the SC state is topologically nontrivial at all. Third, the specific measurement reveals abundance of low energy quasiparticle excitations below the transition temperature. [17] This would point to mu...

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Spin Density Wave Fluctuations andp-Wave Pairing inSr2RuO4

Cited by 41 publications

References 29 publications

Absence of a Large Superconductivity-Induced Gap in Magnetic Fluctuations of Sr2RuO4

Absence of a Large Superconductivity-Induced Gap in Magnetic Fluctuations of Sr2RuO4

Is the anisotropy of the upper critical field of Sr₂RuO₄consistent with a helicalp-wave state?

Theory of superconductivity in a three-orbital model of Sr ₂ RuO ₄

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Spin Density Wave Fluctuations andp-Wave Pairing inSr2RuO4

Cited by 41 publications

References 29 publications

Absence of a Large Superconductivity-Induced Gap in Magnetic Fluctuations of Sr2RuO4

Absence of a Large Superconductivity-Induced Gap in Magnetic Fluctuations of Sr2RuO4

Is the anisotropy of the upper critical field of Sr2RuO4consistent with a helicalp-wave state?

Theory of superconductivity in a three-orbital model of Sr 2 RuO 4

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Is the anisotropy of the upper critical field of Sr₂RuO₄consistent with a helicalp-wave state?

Theory of superconductivity in a three-orbital model of Sr ₂ RuO ₄