Observable NMR signal from circulating current order in YBCO

Lederer, Samuel; Kivelson, Steven A.

doi:10.1103/physrevb.85.155130

Cited by 26 publications

(38 citation statements)

References 11 publications

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“…Our results challenge them as it remains ∼40° whatever the L value. It actually does not favour models in which θ goes to zero at L =0, such as LC models that include apical oxygens as an explanation for the tilt2324, where one would expect a L -dependent tilt. More generally, the observed temperature dependence of θ is not consistent with theories where the tilt direction is due to rigid geometrical factors.…”

Section: Discussionmentioning

confidence: 97%

“…In contrast, the correlated in-plane component develops only below T mag giving rise to an apparent tilt of the magnetic moment. Most theories that are interpretating the origin of the tilt, θ , focus on the Bragg peak L =1 (refs 24, 28, 29). Our results challenge them as it remains ∼40° whatever the L value.…”

Section: Discussionmentioning

confidence: 99%

“…While out-of-plane magnetic moments should be produced by the planar confinement of LC, the observed magnetic moments also display an unexpected in-plane component, giving rise to a tilt of ∼45° with respect to c axis591112 at low temperature. Several attempts to explain this observation were proposed: an additional spin response through spin-orbit coupling22; a geometrical tilt of moment through delocalization of the LC over CuO octahedra or pyramids2324; and a superposition of LC states through quantum effects25. Beside the LC model, electronic phases that break time-reversal symmetry, but preserve LTS, were proposed to pre-empt either a pair density wave state26 or a composite charge density wave (CDW) state27.…”

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confidence: 99%

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Intra-unit-cell magnetic correlations near optimal doping in YBa2Cu3O6.85

et al. 2015

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The pseudo-gap phenomenon in copper oxide superconductors is central to any description of these materials as it prefigures the superconducting state itself. A magnetic intra-unit-cell order was found to occur just at the pseudo-gap temperature in four cuprate high-Tc superconducting families. Here we present polarized neutron-scattering measurements of nearly optimally doped YBa2Cu3O6.85, carried out on two different spectrometers, that reveal several features. The intra-unit-cell order consists of finite-sized planar domains that are very weakly correlated along the c axis. At high temperature, only the out-of-plane magnetic components correlate, indicating a strong Ising anisotropy. An aditional in-plane response develops at low temperature, giving rise to an apparent tilt of the magnetic moment. The discovery of these two regimes puts stringent constraints, which are tightly bound to the pseudo-gap physics, on the intrinsic nature of intra-unit-cell order.

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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Intra-unit-cell magnetic correlations near optimal doping in YBa2Cu3O6.85

et al. 2015

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“…A more stringent test, if the orbital currents have the symmetry shown in Fig.1, is to examine the NMR linewidth for broadening that might reflect a small frequency splitting. Our measurements at all temperatures of the angular variation of the linewidth is less than 0.5 kHz which places a bound on orbital current fields of 0.4 G. According to Lederer and Kivelson,[19] orbital currents inferred from neutron scattering results [8,10,11] should lead to local fields of order H max ∼ 200 G oriented as indicated in Fig.1. Taken together, our measurements of the angular variations of the apical orbital shift and NMR linewidth, in-plane and out of-plane, place substantial constraints on predictions from the theory for a static orbital field to be less than 0.4 G.…”

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confidence: 83%

Absence of Static Loop-Current Magnetism at the Apical Oxygen Site inHgBa2CuO4+δfrom NMR

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Lee

et al. 2013

Phys. Rev. Lett.

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The simple structure of HgBa2CuO 4+δ (Hg1201) is ideal among cuprates for study of the pseudogap phase as a broken symmetry state. We have performed 17 O nuclear magnetic resonance (NMR) on an underdoped Hg1201 crystal with transition temperature of 74 K to look for circulating orbital currents proposed theoretically and inferred from neutron scattering. The narrow spectra preclude static local fields in the pseudogap phase at the apical site, suggesting that the moments observed with neutrons are fluctuating. The NMR frequency shifts are consistent with a dipolar field from the Cu +2 site. [14] show the appearance of broken time reversal symmetry that correlates with the onset of the pseudogap phase with a magnetic moment tilted away from the crystalline c-axis. A muon spin relaxation (µSR) experiment in zero field was unable to detect this magnetism [15] although screening effects may account for muon insensitivity. [16] To account for neutron data, extensions of 2D orbital currents to 3D models have been proposed which include the apical oxygen[17] as well as a quantum mechanical calculation [18] which has an out-of-plane component with a tilted local field. In this context, magnetic fields at the apical oxygen site, Fig.1(a) 89 Y is in a symmetry position which is insensitive to orbital current ordering and neutron data is not available in these materials for direct comparison. We report here our investigation of local fields in Hg1201 with 17 O NMR for which the apical oxygen is sensitive to orbital currents and polarized neutron scattering show evidence for magnetic ordering.Until recently, NMR results for Hg1201 have been constrained to c-axis magnetically aligned powdered samples, [22][23][24][25] which are more easily annealed and have a large NMR signal. However, these powder samples are disordered in the ab-plane and they can have a larger spectral linewidth due to imperfect alignment. In order to investigate possible effects of orbital currents, high arXiv:1304.6415v1 [cond-mat.supr-con]

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“…In addition, the Θ II phase (a q = 0 Fermi surface instability) faces the challenge of explaining the excitation gap in the pseudogap regime. Intense effort has been devoted to searching indirectly for orbital loop currents, using techniques such as NMR [47][48][49] and muon spin rotation, [50][51][52] but their existence in the cuprates remains inconclusive.…”

Section: Introductionmentioning

confidence: 99%

Numerical exploration of spontaneous broken symmetries in multiorbital Hubbard models

et al. 2014

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We study three proposals for broken symmetry in the cuprate pseudogap -oxygen antiferromagnetism, ΘII orbital loop currents, and circulating currents involving apex oxygens -through numerical exploration of multi-orbital Hubbard models. Our numerically exact results show no evidence for the existence of oxygen antiferromagnetic order or the ΘII phase in the three-orbital Hubbard model. The model also fails to sustain an ordered current pattern even with the presence of additional apex oxygen orbitals. We thereby conclude that it is difficult to stabilize the aforementioned phases in the multi-orbital Hubbard models for parameters relevant to cuprate superconductors. However, the ΘII phase might be stabilized through explicit flux terms. We find an enhanced propensity for circulating currents with such terms in calculations simulating applied stress or strain, which skew the copper-oxygen plane to resemble a kagome lattice. We propose an experimental viewpoint to shed additional light on this problem.

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Observable NMR signal from circulating current order in YBCO

Cited by 26 publications

References 11 publications

Intra-unit-cell magnetic correlations near optimal doping in YBa2Cu3O6.85

Intra-unit-cell magnetic correlations near optimal doping in YBa2Cu3O6.85

Absence of Static Loop-Current Magnetism at the Apical Oxygen Site inHgBa2CuO4+δfrom NMR

Numerical exploration of spontaneous broken symmetries in multiorbital Hubbard models

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