Reduction of the 17O Knight Shift in the Superconducting State and the Heat-up Effect by NMR Pulses on Sr2RuO4

Ishida, K.; Manago, Masahiro; Kinjo, Katsuki; Maeno, Y.

doi:10.7566/jpsj.89.034712

Cited by 165 publications

(134 citation statements)

References 38 publications

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“…The first candidate chiral p-wave superconductor is Sr 2 RuO 4 evidenced by previous NMR measurements 8,9 , which breaks the time-reversal symmetry 10 . However, a recent NMR measurement contradicts the previous finding ascribing to the heat-up effect in Knight shift in the NMR experiments 11,12 .…”

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confidence: 81%

Evidence for ferromagnetic order in the CoSb layer ofLaCoSb2

et al. 2020

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The emergence of unconventional superconductivity is generally considered to be related with magnetic spin fluctuations. Unveiling the intriguing behaviours of magnetic spin fluctuations in mother compounds with layered transition metal ions may shed light on the search for exotic superconductors. Here, based on the framework of the first-principles calculations, we theoretically propose the LaCoSb2 as a candidate mother compound of cobalt-based superconductors, which is a weak antiferromagnetic layered metal but has an in-plane ferromagnetic order of 0.88 µB on Co sites. Importantly, this theoretical finding is supported by our magnetization measurements on polycrystalline samples of the LaCoSb2 experimentally. These results imply a possible p-wave superconductor hosted in the LaCoSb2, once the emergence of superconductivity locates in the vicinity of the verge of the ferromagnetic order, having potential applications in topological quantum computing in future.Introduction.-The studies on the topological superconductors 1-3 have triggered enormous research interests during the recent years, ascribing to these systems hosted the Majorana quasiparticles 4 , which obey non-Abelian statistics and can be used to encode and manipulate quantum information in a topologically protected manner 5 . In solid state systems, the p-wave superconductors 6 or ν = 5 2 fractional quantum Hall states 7 are considered to exhibit Majorana quasiparticles. The first candidate chiral p-wave superconductor is Sr 2 RuO 4 evidenced by previous NMR measurements 8,9 , which breaks the time-reversal symmetry 10 . However, a recent NMR measurement contradicts the previous finding ascribing to the heat-up effect in Knight shift in the NMR experiments 11,12 .Alternatively, a prominent theoretical study predicts the appearance of Majorana bound states at the interface between a topological insulator and a conventional superconductor 13 . A generic theory without any topological insulator is also proposed that considering the combination of Rashba spin-orbit coupling and Zeeman effect as well as the proximity effect from an s-wave superconductor in a two-dimensional metal will induce an effective p-wave superconductor 14 . Experimentally, the indictions of Majorana bound states have been reported in various systems, including the indium antimonide nanowires in contact with the superconductor 15,16 , at the edges of a chain of iron atoms formed on the surface of superconducting lead 17 , quantum spin liquids 18 , and a quantum anomalous Hall effect/supercondctor hybrid device 19 , as well as iron-based superconductors 20 .In this Letter, we theoretically propose the LaCoSb 2

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confidence: 81%

Evidence for ferromagnetic order in the CoSb layer ofLaCoSb2

et al. 2020

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“…The evidence of a two-component SC order parameter 16,17 is difficult to reconcile with the lack of singular T c dependence on symmetry breaking strain 18 or in-plane magnetic field 19 . The evidence of triplet (odd parity 20 ) pairing is difficult to reconcile with the evidence of singlet pairing from nuclear magnetic resonance (NMR) 21,22 and from the fact that the in-plane critical field appears to be Pauli-limited 19 .…”

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confidence: 98%

A proposal for reconciling diverse experiments on the superconducting state in Sr2RuO4

et al. 2020

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A variety of precise experiments have been carried out to establish the character of the superconducting state in Sr 2 RuO 4. Many of these appear to imply contradictory conclusions concerning the symmetries of this state. Here we propose that these results can be reconciled if we assume that there is a near-degeneracy between a d x 2 Ày 2 (B 1g in group theory nomenclature) and a g xyðx 2 Ày 2 Þ (A 2g) superconducting state. From a weak-coupling perspective, such an accidental degeneracy can occur at a point at which a balance between the on-site and nearest-neighbor repulsions triggers a d-wave to g-wave transition.

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“…In view of the Knight-shift experiments [31,32], it is important to comment on the spin susceptibility associated with the dominant E g { [6,3], − [5,3]} channel. Since it is a spin-triplet state with in-plane spin polarization of the Copper pairs, similar to the familiar chiral p-wave spin-triplet pairing with a d vector along the k z direction, it might naively be expected to show a temperature-independent spin susceptibility for inplane fields.…”

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Stabilizing even-parity chiral superconductivity in Sr2RuO4

Suh

Menke

Brydon

et al. 2020

Phys. Rev. Research

134

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Strontium ruthenate (Sr 2 RuO 4) has long been thought to host a spin-triplet chiral p-wave superconducting state. However, the singletlike response observed in recent spin-susceptibility measurements casts serious doubts on this pairing state. Together with the evidence for broken time-reversal symmetry and a jump in the shear modulus c 66 at the superconducting transition temperature, the available experiments point towards an evenparity chiral superconductor with k z (k x ± ik y)-like E g symmetry, which has consistently been dismissed based on the quasi-two-dimensional electronic structure of Sr 2 RuO 4. Here, we show how the orbital degree of freedom can encode the two-component nature of the E g order parameter, allowing for a local orbital-antisymmetric spintriplet state that can be stabilized by on-site Hund's coupling. We find that this exotic E g state can be energetically stable once a complete, realistic three-dimensional model is considered, within which momentum-dependent spin-orbit coupling terms are key. This state naturally gives rise to Bogoliubov Fermi surfaces.

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Reduction of the ¹⁷O Knight Shift in the Superconducting State and the Heat-up Effect by NMR Pulses on Sr₂RuO₄

Cited by 165 publications

References 38 publications

Evidence for ferromagnetic order in the CoSb layer ofLaCoSb2

Evidence for ferromagnetic order in the CoSb layer ofLaCoSb2

A proposal for reconciling diverse experiments on the superconducting state in Sr2RuO4

Stabilizing even-parity chiral superconductivity in Sr2RuO4

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