Inhomogeneity of charge-density-wave order and quenched disorder in a high-[T.sub.c] superconductor

• Published in: Nature (London) 2015-09, p.359
• Main Authors: Campi, G, Bianconi, A, Poccia, N, Bianconi, G, Barba, L, Arrighetti, G, Innocenti, D, Karpinski, J, Zhigadlo, N.D, Kazakov, S.M, Burghammer, M, Zimmermann, M. v, Sprung, M, Ricci, A
• Format: Article
• Language: English
• Subjects: Electric properties; Electrical conductivity; High temperature superconductors; Measurement
• ISSN: 0028-0836; 1476-4687

It has recently been established that the high-transition-temperature (high-[T.sub.c]) superconducting state coexists with short-range charge-density-wave order (1-11) and quenched disorder (12, 13) arising from dopants and strain (14-17). This complex, multiscale phase separation (18-21) invites the development of theories of high-temperature superconductivity that include complexity (22-25). The nature of the spatial interplay between charge and dopant order that provides a basis for nanoscale phase separation remains a key open question, because experiments have yet to probe the unknown spatial distribution at both the nanoscale and mesoscale (between atomic and macroscopic scale). Here we report micro X-ray diffraction imaging of the spatial distribution of both short-range charge-density-wave 'puddles' (domains with only a few wavelengths) and quenched disorder in Hg[Ba.sub.2]Cu[O.sub.4] + y the single-layer cuprate with the highest [T.sub.c], 95 kelvin (refs 26-28). We found that the charge-density-wave puddles, like the steam bubbles in boiling water, have a fat-tailed size distribution that is typical of self-organization near a critical point (19). However, the quenched disorder, which arises from oxygen interstitials, has a distribution that is contrary to the usually assumed random, uncorrelated distribution (12, 13). The interstitial-oxygen-rich domains are spatially anticorrelated with the charge-density-wave domains, because higher doping does not favour the stripy charge-density-wave puddles, leading to a complex emergent geometry of the spatial landscape for superconductivity.