title: The microscopic structure of charge density waves in underdoped YBa2Cu3O6.54 revealed by X-ray diffraction.
abstract: Charge density wave (CDW) order appears throughout the underdoped high-temperature cuprate superconductors, but the underlying symmetry breaking and the origin of the CDW remain unclear. We use X-ray diffraction to determine the microscopic structure of the CDWs in an archetypical cuprate YBa2Cu3O6.54 at its superconducting transition temperature ∼ 60 K. We find that the CDWs in this material break the mirror symmetry of the CuO2 bilayers. The ionic displacements in the CDWs have two components, which are perpendicular and parallel to the CuO2 planes, and are out of phase with each other. The planar oxygen atoms have the largest displacements, perpendicular to the CuO2 planes. Our results allow many electronic properties of the underdoped cuprates to be understood. For instance, the CDWs will lead to local variations in the electronic structure, giving an explicit explanation of density-wave states with broken symmetry observed in scanning tunnelling microscopy and soft X-ray measurements.
authors.affiliation: School of Physics &Astronomy, University of Birmingham, Birmingham B15 2TT, UK.
authors.forename: E M
authors.initials: EM
authors.lastname: Forgan
authors.affiliation: School of Physics &Astronomy, University of Birmingham, Birmingham B15 2TT, UK.
authors.forename: E
authors.initials: E
authors.lastname: Blackburn
authors.affiliation: School of Physics &Astronomy, University of Birmingham, Birmingham B15 2TT, UK.
authors.forename: A T
authors.initials: AT
authors.lastname: Holmes
authors.affiliation: School of Physics &Astronomy, University of Birmingham, Birmingham B15 2TT, UK.
authors.forename: A K R
authors.initials: AK
authors.lastname: Briffa
authors.affiliation: Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Chang
authors.affiliation: XMaS, European Synchrotron Radiation Facility, B.P. 220, Grenoble F-38043, France.|Department of Physics, University of Liverpool, L69 3BX Liverpool, UK.
authors.forename: L
authors.identifier: http://orcid.org/0000-0002-9466-5956
authors.initials: L
authors.lastname: Bouchenoire
authors.affiliation: XMaS, European Synchrotron Radiation Facility, B.P. 220, Grenoble F-38043, France.|Department of Physics, University of Liverpool, L69 3BX Liverpool, UK.
authors.forename: S D
authors.initials: SD
authors.lastname: Brown
authors.affiliation: Department of Physics &Astronomy, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1.
authors.forename: Ruixing
authors.initials: R
authors.lastname: Liang
authors.affiliation: Department of Physics &Astronomy, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1.
authors.forename: D
authors.initials: D
authors.lastname: Bonn
authors.affiliation: Department of Physics &Astronomy, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1.
authors.forename: W N
authors.initials: WN
authors.lastname: Hardy
authors.affiliation: Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
authors.forename: N B
authors.initials: NB
authors.lastname: Christensen
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, 22603 Hamburg, Germany.
authors.forename: M V
authors.initials: MV
authors.lastname: Zimmermann
authors.affiliation: Condensed Matter Physics &Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: M
authors.initials: M
authors.lastname: Hücker
authors.affiliation: H. H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, UK.
authors.forename: S M
authors.initials: SM
authors.lastname: Hayden