Collective Modes in the Loop Current Ordered Phase of Cuprates

Abstract

Recently two branches of weakly dispersive collective modes have been discovered in under-doped cuprates by inelastic neutron scattering. Polarization analysis reveals that the modes are magnetic excitations. They are only visible for temperatures below the transition temperature to a broken symmetry phase which was discovered earlier and their intensity increases as temperature is further decreased. The broken symmetry phase itself has symmetries consistent with ordering of orbital current loops within a unit-cell without breaking translational symmetry. In order to calculate the collective modes of such a state we add quantum terms to the Ashkin-Teller (AT) model with which the classical loop current order has been described. We derive that the mean field ground state of the quantum model is a product over all unit-cells of linear combination of the four possible classical configurations of the loop current order in each unit-cell. The collective modes are calculated by using a generalized Holstein-Primakoff boson representation of orbital moment operators and lead to three branches of gapped weakly dispersive collective modes. The experimental results are consistent with the two lower energy branches; the third mode is at a higher energy than looked for by present neutron scattering experiments and might also be over-damped. Implications of the discovery of the collective modes are discussed.

16 pages, 6 figures

References in corpus (8)

• Magnetic order in the pseudogap phase of high-$T_C$ superconductors
• Hidden magnetic excitation in the pseudogap phase of a model cuprate superconductor
• 2D orbital-like magnetic order in $\mathrm{L}{\mathrm{a}}_{2-\mathrm{x}}\mathrm{S}{\mathrm{r}}_{\mathrm{x}}\mathrm{Cu}{\mathrm{O}}_4$
• Thermodynamic Properties near the onset of Loop-Current Order in high-$T_c$ superconducting cuprates
• Collective Modes in the Loop Ordered Phase of Cuprates
• Magneto-oscillations in Underdoped Cuprates
• Long Wavelength Correlations and Transport in a Marginal Fermi Liquid
• Effective theory of fluctuating circulating currents in high-Tc cuprates

Cited by in corpus (6)

• Hartree-Fock Computation of the High-Tc Cuprate Phase Diagram
• Quantum-Critical Fluctuations in 2D Metals: Strange Metals and Superconductivity in Antiferromagnets and in Cuprates
• Proposed Chiral Texture of the Magnetic Moments of Unit-Cell Loop Currents in the Pseudogap Phase of Cuprate Superconductors
• Evolution of the Superconductivity Dome in the two dimensional Hubbard Model
• Broken relationship between superconducting pairing interaction and electronic dispersion kinks in LSCO
• Theory of Polarized Neutron Scattering in the Loop Ordered Phase of Cuprates