Scanning micro-x-ray diffraction unveils the distribution of oxygen chain nanoscale puddles in YBa2Cu3O6.33

Abstract

Oxygen chain fragments are known to appear at the insulator-to-superconductor transition in YBa 2 Cu 3 O 6+y . However, the self-organization and the size distribution of oxygen chain fragments are not known. Here, we seek to fill this gap, using scanning micro-x-ray diffraction, which is an imaging method based on advances in focusing a synchrotron radiation beam. This approach allows us to probe both real-space and k-space of high-quality YBa 2 Cu 3 O 6.33 single crystals with T c = 7 K. We report compelling evidence for nanoscale striped puddles, with Ortho-II structure, made of chain fragments in the basal Cu(1) plane with local oxygen concentration y 0.5. The size of the Ortho-II puddles spans a range between 2 and 9 nm. The real-space imaging of Ortho-II puddles granular network shows that superconductivity, at a low hole-doping regime, occurs in a network of nanoscale oxygen ordered patches, interspersed with oxygen depleted regions. The manipulation by thermal treatments of the striped Ortho-II puddles has been investigated focusing on the spontaneous symmetry breaking near the order-to-disorder phase transition at T 0 = 350 K.

Fermi surface reconstruction of superoxygenated La2CuO4superconductors with ordered oxygen interstitials

“…[25][26][27] In the underdoped regime of cuprates a structural phase separation between a dopant-poor antiferromagnetic phase and a dopant-rich metallic phase with doping close to 1/8 is clearly observed in La 2 CuO 4+y for 0< y <0.055 28 and YBa 2 Cu 3 O 6+y . 29 In the optimum and high doping regime of cuprates recent high-resolution ARPES and STM experiments [30][31][32] show multiple electronic components with electronic phase separation at low temperature. A first pseudogap phase with doping around 1/8 competes with a highly doped metallic phase with about 1/4 holes per Cu site well described band structure calculations, confirming previous findings of phase separation giving distinct physics beyond the superconducting dome.…”

Two-Dimensional Nanogranularity of the Oxygen Chains in the YBa2Cu3O6.33 Superconductor

“…In order to characterize this spatial texture, we calculated the Probability Density Function of both ξ a and ξ b (see Figure 2c). As previously determined by statistical analysis of domain sizes, some deviations from normal behavior are observed in the right tails of distribution [27][28][29][30]. These deviations can be quantified by the distribution skewness, sk, giving sk a =1.35 and sk b =28.5 for the Ortho-II domain size along the a and b directions, respectively.…”

“…This makes the study of quenched disorder and its spatial distribution of fundamental importance. This ordering gives rise to "guest superstructures" detected as satellite peaks in diffraction patterns [26][27][28][29][30].…”

“…The spatial distribution of different superstructures have been investigated by us using X ray diffraction in reflection mode, probing the vertical plane ac [27,30].…”

Nanoscale Dynamics in Complex Materials by Resonant X-Ray Photon Correlation Spectroscopy (rXPCS)

“…On this purpose an important solution came from the use of innovative techniques like scanning micro X-ray diffraction (SµXRD) and resonant scanning micro X-ray diffraction (rSµXRD) that allow to directly visualize the bulk spatial organization of the SDW, CDW and defects puddles. Indeed by the use of SµXRD on several High temperature superconductors (HTS) it has been possible to directly visualize a complex nanoscale phase separation characterized by the coexistence of competing granular networks of different puddles [11][12][13][14][15][16][17][18][19][20][21] forming a complex organization like in social networks [22]. The use of SµXRD has even allowed to demonstrate that an optimum inhomogeneity is needed to promote the percolation of one of the present phases in the material [23] characterized by a critical misfit-strain [24][25][26].…”