Abstract
While it is known that the nature and the arrangement of defects in complex oxides have an impact on the material functionalities, little is known about control of superconductivity by oxygen interstitial organization in cuprates. Here we report direct compelling evidence for the control of Tc by manipulation of the superconducting granular networks of nanoscale puddles, made of ordered oxygen stripes, in a single crystal of YBa2Cu3O6.5 + y with average formal hole doping p close to 1/8. Upon thermal treatments we were able to switch from a first network of oxygen defect striped puddles with OVIII modulation (qOVIII(a*) = (h + 3/8, k, 0) and qOVIII(a*) = (h + 5/8, k, 0)) to a second network characterized by OXVI modulation (qOXVI(a*) = (h + 7/16, k, 0) and qox-VI(a*) = (h + 9/16, k, 0)) and finally to a third network with puddles of OV periodicity (qOV(a*) = (4/10, 1, 0) and qOV(a*) = (6/10, 1, 0)). We map the microscopic spatial evolution of the out of plane OVIII, OXVI and OV puddle nano-size distribution via scanning micro-diffraction measurements. In particular, we calculated the number of oxygen chains (n) and the charge density (hole concentration p) inside each puddle, analyzing areas of 160 × 80 μm2, and recording 12 800 diffraction patterns to reconstruct each spatial map. The high spatial inhomogeneity shown by all the reconstructed spatial maps reflects the intrinsic granular structure that characterizes cuprates and iron chalcogenides, disclosing the presence of several complex networks of coexisting superconducting domains with different lattice modulations, charge densities and gaps as in the proposed multi-gap scenario called superstripes.
Highlights
An essential step towards the understanding of modern materials and their implementation in novel nano-electronic devices is the control and manipulation of their microscopic behavior [1,2,3]
We mapped with micrometric resolution the out of plane domain size, the number of oxygen chains and the charge density inside each domain, covering a total area of 160 × 80 μm2
Reductions in the out of plane domain size, in the number of oxygen chains and in the microscopic distribution of charge density have been observed in the OV phase
Summary
An essential step towards the understanding of modern materials and their implementation in novel nano-electronic devices is the control and manipulation of their microscopic behavior [1,2,3]. Novel results obtained in YBa2Cu3O6 + y (YBCO) provide compelling evidence for charge density waves (CDWs), and static magnetic stripes are intertwined and aggregated in nanoscale puddles [16,17,18,19,20,21] These domains are spatially separated by superconducting regions composed by ordered lattice stripes [22,23,24,25,26] forming an intrinsically complex lattice of striped puddles called the ‘superstripe’ scenario [13]. In this scenario the local lattice modulations determine multiple subbands crossing the Fermi level and multi-gap superconductivity below the critical temperature [27, 28]. Due to the lack of proper local bulk-sensitive probes, the microscopic scenario is still not clear and the real-space and real-time observation of thermally induced rearrangements of superconducting microregions in HTS is a difficult experimental task
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