Loop currents in quantum matter

Bourgès, Philippe; Bounoua, Dalila; Sidis, Y.

doi:10.5802/crphys.84

Cited by 27 publications

(24 citation statements)

References 111 publications

(372 reference statements)

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“…A variety of experiments are now consistent [31][32][33][34][35][36][37][38][39][40][41] with the predicted broken symmetry in cuprates, while the broken symmetry relevant to the quantum-fluctuations in the heavy-fermions and other metallic antiferromagnets is of-course obvious. Further experiments are required to ascertain predicted broken symmetry [42,43] in TBG and TBWSe.…”

Section: Introductionmentioning

confidence: 86%

Quantum-critical conductivity of marginal Fermi-liquids

Maebashi¹,

Varma²

2022

Preprint

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We present exact results for the electrical and thermal conductivity at low temperatures and frequencies in the quantum-critical region for fermions on a lattice scattering with the collective fluctuations of the quantum xy model. The model is applicable to the fluctuations of the loop-current order in cuprates as well as to a class of quasi-two dimensional heavy-fermion and other metallic antiferromagnets, and proposed recently also for the possible loop-current order in Moiré twisted bi-layer graphene, and for WSe 2 . All these metals have a linear in temperature electrical resistivity in the quantum-critical region of their phase diagrams, often termed "Planckian" resistivity. The solution of the integral equation for the vertex in the Kubo equation for transport shows that all vertex renormalizations except due to Aslamazov-Larkin processes are absent.The latter appear as an Umklapp scattering matrix, which is shown to give only a temperature independent multiplicative factor for electrical conductivity which is non-zero in the pure limit only if the Fermi-surface is large enough. We also show that the vertex renormalization and the logarithmic enhancement of the marginal Fermi-liquid specific heat do not appear in the thermal conductivity. The results for transport properties are derived for any Fermi-surface on any two-dimensional lattice. As an example, the numerical factor in the linear in T resistivity is explicitly calculated for large enough circular Fermi-surfaces on a square lattice.

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Section: Introductionmentioning

confidence: 86%

Quantum-critical conductivity of marginal Fermi-liquids

Maebashi¹,

Varma²

2022

Preprint

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“…Polarization analysis measures the magnetic content of a Bragg spot with overlapping nuclear and magnetic amplitudes, which occurs when the magnetic motif and chemical structure coincide [16,20]. Primary and secondary polarizations are denoted P and P , and a fraction (1 − P • P )/2 of neutrons participate in events that change (flip) the neutron spin orientation.…”

Section: Magnetic Neutron Diffractionmentioning

confidence: 99%

“…electronic multipoles. An intra-unit-cell loop current order [13,16], likewise breaking both parity and time-reversal symmetries, is fundamentally different from one derived directly from a symmetry-informed magnetic structure. For, the former type of order uses nebulous loop currents circulating coherently between vanadium and ligand orbitals, whereas our magnetic order is built with local vanadium electronic multipoles with defined discrete symmetries decorating a lattice.…”

Section: Introductionmentioning

confidence: 99%

“…Likewise in the case of ceramic superconductor materials, where copper Dirac multipoles furnish a good account of magnetism in the pseudogap phase. The value of the successful analysis of a neutron Bragg diffraction pattern from Hg1201 has been bolstered by a microscopic account of the formation of the relevant magnetic order parameter [14][15][16]. Specifically, anti-inversion symmetry in Cu sites emerges from centrosymmetric sites in the parent chemical structure.…”

Section: Introductionmentioning

confidence: 99%

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Hidden magnetic order on a kagome lattice for KV3Sb5

Scagnoli

Khalyavin²,

Lovesey

2022

Phys. Rev. B

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KV 3 Sb 5 has recently attracted considerable attention due to its low-temperature superconducting properties, which are heralded by a charge-density wave. The apparent presence of a very weak magnetism does not result in long-range ordering. An explanation of the properties we present invokes higher-order terms in the vanadium magnetization density and a "hidden order" of Dirac (polar) multipoles. The Dirac dipole, known as an anapole or toroidal dipole, is one of a family of electronic multipoles visible in x-ray and magnetic neutron diffractions while undetectable with standard laboratory-based techniques. Actually, two viable magnetic structures, direct descendants of the established chemical structure, are studied with a view to testing their suitability in future experiments. One model structure is magnetoelectric and restricted to the linear type, whereas a second model cannot show a magnetoelectric effect of any type. The latter hosts a strange vanadium entity that is a true scalar and magnetic (time-odd), and associated in our paper with a fictitious charge distribution that is purely imaginary. Calculated x-ray and neutron-scattering amplitudes are symmetry-informed expressions of vanadium Dirac multipoles. Bragg diffraction patterns for the two models are found to be distinctly different, fortunately. Likewise, magnetochiral signals derived from our x-ray scattering amplitudes.

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“…Apart from the multiferroic nature in the ICM phase, CuO has been proposed to have an orbital current in the CM phase [14]. The orbital current is characterized by a time-odd polar vector corresponding to an anapole or toroidal moment [15] and is proposed as the order parameter in the pseudogap phase of high-T C cuprate superconductors [16,17] and the hidden ordered phase in Sr 2 (Ir, Rh)O 4 [18]. Scagnoli et al [14] performed a resonant x-ray diffraction (RXD) measurement at the Cu L 3 edge on CuO in the CM phase.…”

Section: Introductionmentioning

confidence: 99%

Magnetic domains in two distinct antiferromagnetic phases of CuO

et al. 2022

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Multiferroic CuO showing two distinct antiferromagnetic (AFM) phases: incommensurate (ICM) spiral and commensurate (CM) collinear AFM phases, is investigated by resonant x-ray diffraction (RXD) at the Cu L 3 edge. In the ICM phase where spin-spiral-induced ferroelectricity develops, circular dichroism ascribed to the handedness of the spiral magnetic order is observed at the magnetic Bragg (0.506, 0, −0.483) reflection. By measuring two-dimensional maps of the reflection intensity, the spatial distribution of the ferroelectric domains is clarified and is found to be strongly influenced by crystallographic twin structures. In the CM phase, weaker but substantial circular dichroic signals are observed at the magnetic Bragg (0.5, 0, −0.5) reflection. It is found that the spatial distributions of the circular dichroic signals resemble those in the ICM phase, suggesting some relation between the ICM and CM phases. The origin of the circular dichroic RXD observed in CuO is discussed based on the experimental observations.

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Loop currents in quantum matter

Cited by 27 publications

References 111 publications

Quantum-critical conductivity of marginal Fermi-liquids

Quantum-critical conductivity of marginal Fermi-liquids

Hidden magnetic order on a kagome lattice for KV3Sb5

Magnetic domains in two distinct antiferromagnetic phases of CuO

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