Impact of Quenched Oxygen Disorder on Charge Density Wave Order inYBa2Cu3O6+x

Abstract

The competition between superconductivity and charge density wave (CDW) order in underdoped cuprates has now been widely reported, but the role of disorder in this competition has yet to be fully resolved. A central question is whether disorder sets the length scale of the CDW order, for instance by pinning charge density fluctuations or disrupting an otherwise long range order. Using resonant soft x-ray scattering, we investigate the sensitivity of CDW order in YBa2Cu3O6+x (YBCO) to varying levels of oxygen disorder. We find that quench cooling YBCO6.67 (YBCO6.75) crystals to destroy their o-V and o-VIII (o-III) chains decreases the intensity of the CDW superlattice peak by a factor of 1.9 (1.3), but has little effect on the CDW correlation length, incommensurability, and temperature dependence. This reveals that while quenched oxygen disorder influences the CDW order parameter, the spatial extent of the CDW order is insensitive to the level of quenched oxygen disorder and may instead be a consequence of competition with superconductivity.Charge density wave (CDW) order has been solidified as a generic property and principal competitor to superconductivity (SC) [5] Within such interpretations, the common short range character of CDW order in the cuprates is associated with each material's specific defect properties and crystal structure. However, it is also possible that such descriptions only apply due to the high defect strength, masking a more generic and intrinsic origin of this length scale, such as the competition of CDW order with superconductivity. [20,21] To address this question, we turn to high-purity, oxygen ordered YBCO. With regards to defects, YBCO represents a special case in the cuprates since stoichiometric, ultra-high purity crystals can be grown with low levels of cation disorder.[22] Doping of the CuO 2 planes occurs by the addition of oxygen atoms into the chain layer, which can organize into a number of ortho-ordered phases depending on the oxygen content. [23][24][25] Disorder in these CuO chains have been shown by microwave conductivity studies of quasiparticle scattering in YBCO 6.5 to be the dominant source of weak-limit scattering, [26] indicating that the most influential defects in YBCO reside in the chain layer.[15] As previously established, the oxygen ordered states can be intentionally destroyed by heating YBCO crystals to modest temperatures and subsequently quench cooling to prevent the formation of chain order. [25][26][27][28] This allows for individual crystals of YBCO to be investigated with varying degrees of disorder.In this Letter, we exploit this means of controlling disorder in YBCO to study the effect of quenched disorder on CDW order in the cuprates using resonant soft x-ray scattering (RSXS). Our main finding is that disordering the chains decreases the CDW scattering intensity, but has little impact on the CDW correlation length (ξ CDW ), incommensurability or T dependence. This reveals that while disorder influences the CDW order parameter, the length scale of...

Long-range order and pinning of charge-density waves in competition with superconductivity

“…6 Another discrepancy exists with Ref. 9, where S CDW was found to decrease upon increasing the amount of oxygen disorder.…”

Enhanced coherent oscillations in the superconducting state of underdopedYBa2Cu3O6+x

“…The sample [19] was single-crystal YBa 2 Cu 3 O 6+x with ortho-III oxygen ordering [20], with x = 0.75. The critical temperature (T c ) for the superconducting transition is 75.2 K and the doping level is p = 0.133.…”

“…The high-quality detwinned single crystals of YBCO are platelets with the broad face perpendicular to the c axis, and were measured with the polarization along either the a or b crystallographic directions. The CDW transition temperature T CDW was found to occur at ∼150 K using resonant x-ray scattering [20]. Strong, single-cycle THz pulses were generated from a LiNbO 3 crystal via optical rectification of 800 nm femtosecond laser pulses using the tilted-phase front technique [21].…”

Broken translational and rotational symmetry via charge stripe order in underdoped YBa 2 Cu 3 O 6+ y

“…• In addition to these aspects, a recent study by Achkar et al [47] directly showed that the CDW correlations are to a large degree unaffected upon disordering the CuO chains, and therefore are intrinsic to the CuO 2 planes. This once again validates the scenario where the ordering mechanisms in the planes are largely insensitive to the phenomenology in the chain layer, where the orthorhombicity originates from.…”