title: a-b Anisotropy of the Intra-Unit-Cell Magnetic Order in YBa_{2}Cu_{3}O_{6.6}.
abstract: Within the complex phase diagram of the hole-doped cuprates, seizing the nature of the mysterious pseudogap phase is essential for unraveling the microscopic origin of high-temperature superconductivity. Below the pseudogap temperature T^{⋆}, evidence for intra-unit-cell orders breaking the fourfold rotation symmetry have been provided by neutron diffraction and scanning tunneling spectroscopy. Using polarized neutron diffraction on a detwinned YBa_{2}Cu_{3}O_{6.6} sample, we here report a distinct a-b anisotropy of the intra-unit-cell magnetic structure factor below T^{⋆}, highlighting that intra-unit-cell order in this material breaks the mirror symmetry of the CuO_{2} bilayers. This is likely to originate from a crisscrossed arrangement of loop currents within the CuO_{2} bilayer, resulting in a bilayer mean toroidal axis along the b direction.
authors.affiliation: Laboratoire Léon Brillouin, CEA-CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France.
authors.forename: Lucile
authors.initials: L
authors.lastname: Mangin-Thro
authors.affiliation: Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Li
authors.affiliation: Laboratoire Léon Brillouin, CEA-CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France.
authors.forename: Yvan
authors.initials: Y
authors.lastname: Sidis
authors.affiliation: Laboratoire Léon Brillouin, CEA-CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Bourges