Abstract
Incommensurate charge order (CO) has been identified as the leading competitor of high-temperature superconductivity in all major families of layered copper oxides, but the perplexing variety of CO states in different cuprates has confounded investigations of its impact on the transport and thermodynamic properties. The three-dimensional (3D) CO observed in YBa2Cu3O6+x in high magnetic fields is of particular interest, because quantum transport measurements have revealed detailed information about the corresponding Fermi surface. Here we use resonant X-ray scattering to demonstrate 3D-CO in underdoped YBa2Cu3O6+x films grown epitaxially on SrTiO3 in the absence of magnetic fields. The resonance profiles indicate that Cu sites in the charge-reservoir layers participate in the CO state, and thus efficiently transmit CO correlations between adjacent CuO2 bilayer units. The results offer fresh perspectives for experiments elucidating the influence of 3D-CO on the electronic properties of cuprates without the need to apply high magnetic fields.
Highlights
Background subtracted andLorentzian fit 55 KIntensity13 K 50 K 109 K 229 K 342 KL = 1 L = 1.47 Tc = 53 K12 K 55 K 170 K 300 K Tc = 55 K 1000 d–0.38 –0.34 –0.30 H (r.l.u. of YBCO) 53 K 50 K 41 K –0.30 53 K
We investigated underdoped YBCO films of different thicknesses that were grown epitaxially on SrTiO3 (STO) substrates using pulsed laser deposition
A more profound difference between the crystal structure of our YBCO films and that of bulk YBCO is indicated by the absence of any of the conventional CuO chain ordering patterns[24] associated with the charge-reservoir layer in our scattering experiments
Summary
The local orthorhombic distortion of the unit cell caused by the dopant oxygens in the charge-reservoir layer is uncorrelated, and the crystal structure is essentially tetragonal to any non-local probe. This change in lattice symmetry is presumably a consequence of the epitaxial relationship with the STO substrate, which enforces a tetragonal structure in the deposited layers; prior work has shown that such effects can persist over tens of nm in the growth direction[25,26]. Since the 3D-CO is still observable in the 50 nm films at 300 K, fluorescence backgrounds of the type shown, d, f (dashed lines) were subtracted from the 12 K data before fitting. Errors in the tabulated values were estimated from a sensitivity analysis of the various background subtraction procedures
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