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Almeida-Didry, Sonia De; Sidis, Y.; Balédent, V.; Giovannelli, Fabien; Monot‐Laffez, Isabelle; Bourges, P.

doi:10.1103/physrevb.86.020504

Cited by 61 publications

(97 citation statements)

References 43 publications

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“…Polarized neutron scattering in YBa 2 Cu 3 O 7−δ [8][9][10], HgBa 2 CuO 4+δ (Hg1201) [11,12], Bi 2 Sr 2 CaCu 2 O 8+δ [13], and La 2−x Sr x CuO 4 (short ranged) [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.…”

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confidence: 99%

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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confidence: 99%

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

Mounce

Lee

et al. 2013

Phys. Rev. Lett.

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“…Seemingly the strongest experimental evidence for an orbital-current phase are the observations of an unusual translational-symmetry preserving magnetic order in underdoped YBa 2 Cu 3 O 6+x , HgBa 2 CuO 4+δ , La 2−x Sr x CuO 4 , and Bi 2 Sr 2 CaCu 2 O 8+δ by spin-polarized neutron diffraction 6,8 . However, local probes of magnetism, such as nuclear magnetic resonance (NMR) and zero-field muon spin relaxation (ZF-µSR) have found no evidence for the onset of magnetic order at the pseudogap temperature T * 11-13 .…”

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Pseudogap phase in cuprates: Oxygen orbital moments instead of circulating currents

Moskvin

2012

Jetp Lett.

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Circulating current (CC) loops within the cuprate unit cell are proposed to play a key role in the physics of the pseudogap phase. However, main experimental observations motivated by this sophisticated proposal and seemingly supporting the CC model can be explained in frames of a simple and physically clear microscopic model. We argue that instead of a well-isolated Zhang-Rice (ZR) singlet 1 A1g the ground state of the hole center [CuO4] 5− (cluster analog of Cu 3+ ion) in cuprates should be described by a complex 1 A1g-1,3 B2g-1,3 Eu multiplet, formed by a competition of conventional hybrid Cu 3d-O 2p b1g(σ) ∝ d x 2 −y 2 state and purely oxygen nonbonding O 2pπ states with a2g(π) and eux,y(π) symmetry. In contrast with inactive ZR singlet we arrive at several novel competing orbital and spin-orbital order parameters, e.g., Ising-like net orbital magnetic moment, orbital toroidal moment, intra-plaquette's staggered order of Ising-like oxygen orbital magnetic moments. As a most impressive validation of the non-ZR model we explain fascinating results of recent neutron scattering measurements that revealed novel type of magnetic ordering in pseudogap phase of several hole-doped cuprates.

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“…Neutron scattering measurements [29][30][31] provide support for the loop currents shown in Fig. 1(a).…”

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“…1(a) breaks rotational symmetry in the plane as specified by the vector N , the neutron scattering measurements [29][30][31] always observe the full rotational symmetry. This may be due to domains with different N , but the spiral order shown in Fig.…”

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Proposed Chiral Texture of the Magnetic Moments of Unit-Cell Loop Currents in the Pseudogap Phase of Cuprate Superconductors

2013

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We propose a novel chiral order parameter to explain the unusual polar Kerr effect in underdoped cuprates. It is based on the loop-current model by Varma, which is characterized by the in-plane anapole moment N and exhibits the magnetoelectric effect. We propose a helical structure where the vector N (n) in the layer n is twisted by the angle π/2 relative to N (n−1) , thus breaking inversion symmetry. We show that coupling between magnetoelectric terms in the neighboring layers for this structure produces optical gyrotropy, which results in circular dichroism and the polar Kerr effect.PACS numbers: 74.72. Gh, 78.20.Jq, 78.20.Ek Introduction.-The nature of the pseudogap phase in underdoped cuprate superconductors has been a longstanding problem [1]. A series of optical measurements [2-5] revealed gyrotropy in this state. It was observed that the polarizations of incident and reflected light differ by a small angle θ K , called the polar Kerr angle. Initially, these experiments were interpreted as the evidence for spontaneous time-reversal symmetry breaking. Theoretical models [6-9] derived optical gyrotropy from the anomalous Hall effect. In these scenarios, the order parameter is equivalent to an intrinsic magnetic field perpendicular to the layers, which permeates the system and points inward and outward at the opposite surfaces of a crystal. Therefore, the Kerr angle should have opposite signs at the opposite surfaces of the crystal.However, recent reports [10,11] found that the Kerr angle has the same sign at the opposite surfaces of a sample. Therefore, the observed gyrotropy is not consistent with the time-reversal-symmetry breaking due to a magnetic order and should be interpreted as the evidence for natural optical activity due to chiral symmetry breaking [12]. Systems with helical structures, such as cholesteric liquid crystals and some organic molecules, typically exhibit optical gyrotropy and the polar Kerr effect. It is important that the sign of the Kerr angle in this case is the same at the opposite surfaces of the system, in contrast to the gyrotropy produced by a magnetic order (see

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Evidence for intra-unit-cell magnetic order in Bi2Sr2CaCu2O
Sonia De Almeida-Didry
¹
,
Y. Sidis
²
,
V. Balédent
³

et al.

Cited by 61 publications

References 43 publications

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

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

Pseudogap phase in cuprates: Oxygen orbital moments instead of circulating currents

Proposed Chiral Texture of the Magnetic Moments of Unit-Cell Loop Currents in the Pseudogap Phase of Cuprate Superconductors

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Evidence for intra-unit-cell magnetic order in Bi2Sr2CaCu2OSonia De Almeida-Didry1, Y. Sidis2, V. Balédent3 et al.

Cited by 61 publications

References 43 publications

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

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

Pseudogap phase in cuprates: Oxygen orbital moments instead of circulating currents

Proposed Chiral Texture of the Magnetic Moments of Unit-Cell Loop Currents in the Pseudogap Phase of Cuprate Superconductors

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Evidence for intra-unit-cell magnetic order in Bi2Sr2CaCu2O
Sonia De Almeida-Didry
¹
,
Y. Sidis
²
,
V. Balédent
³

et al.