Orbital symmetry of charge-density-wave order in La1.875Ba0.125CuO4 and YBa2Cu3O6.67

Abstract

Recent theories of charge-density-wave (CDW) order in high-temperature superconductors have predicted a primarily d CDW orbital symmetry. Here, we report on the orbital symmetry of CDW order in the canonical cuprate superconductors La1.875Ba0.125CuO4 (LBCO) and YBa2Cu3O6.67 (YBCO), using resonant soft X-ray scattering and a model mapped to the CDW orbital symmetry. From measurements sensitive to the O sublattice, we conclude that LBCO has predominantly s' CDW orbital symmetry, in contrast to the d orbital symmetry recently reported in other cuprates. Furthermore, we show for YBCO that the CDW orbital symmetry differs along the a and b crystal axes and that these both differ from LBCO. This work highlights CDW orbital symmetry as an additional key property that distinguishes the different cuprate families. We discuss how the CDW symmetry may be related to the '1/8-anomaly' and to static spin ordering.

Spin-fermion model with overlapping hot spots and charge modulation in cuprates

“…With different experimental techniques (resonant X-ray scattering, hard X-ray diffraction, scanning tunneling microscopy(STM)) CDWs have been directly detected in underdoped samples of YBCO [1][2][3][4][5][6][7][8][9][10][11] , Bi-2201 12,13 , Bi-2212 [14][15][16][17][18][19] and, recently, Hg-1201 20,21 compounds. Additional input comes from indirect probes, such as transport measurements 22,23 and quantum resistance oscillations [24][25][26] consistent with a CDW-like reconstruction [27][28][29] of the Fermi surface (FS), nuclear magnetic resonance 30,31 , ultrasound propagation 32 and reflectivity oscillations in pump-probe experiments due to a collective CDW mode 33 .…”

Doping asymmetry and striping in a three-orbitalCuO2Hubbard model

“…This pair-density-wave phase is believed to have a d-wave pair-field which is large in the regions with excess holes and oscillates in sign between these charged regions 12,13 . Achkar et al 14 have reported resonant soft x-ray scattering measurements which show that the charge distribution on the oxygens of LBCO have an s -CDW orbital structure in which the charge modulations on the O px and O py sites in a unit cell are in phase. STM Studies of BSCCO (p ∼ 8%) and NaCCOC (p ∼ 12%) find that these materials have a predominantly d-CDW orbital form factor in which these O px and O py charge modulations are out of phase 15 .…”

“…When additional holes are added they go ∼ 75% onto the O sites and charge stripes separated by π-phase shifted antiferromagnetic regions appear. The O hole occupation and the Cu spin structure has an s -CDW-SDW like structure 14 . When additional electrons are added, they go approximately 90% onto the Cu d x 2 −y 2 orbitals.…”

Instability towards staggered loop currents in the three-orbital model for cuprate superconductors

“…The close connection between axial charge order with a d-wave form factor 31 and oxygen orbitals makes the three-band model a necessary starting point for the microscopic theory. In this context, the focus has so far been on spin fluctuations, and hence on the local Coulomb interactions U d and U p .…”

“…The ICO phase involves predominantly a charge transfer between oxygen orbitals in the CuO 2 planes [20][21][22]31,32 . This challenges notions of immutable CuO 2 bands, and points to the necessity to employ multiorbital models for the ICO phase [33][34][35] .…”