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Magnetic neutron scattering, angle-dependent photoemission (ARPES), and
scanning tunneling microscopy (STM) have all found evidence suggestive of
charge ordering in the cuprates. However, whereas the neutron scattering
results are generally interpreted in terms of quasi-one-dimensional
'stripes', recent STM studies find evidence for more two-dimensional
'checkerboard' patterns[1]. Both features display a prominent '4a'
periodicity, suggesting a close connection.
It is known that the neutron scattering results are consistent with having crossed stripes in alternate layers, and here I demonstrate that this can help explain the appearence of checkerboard-like features. For instance, interlayer hopping leads to a modulation of the charge density along one stripe, leading to a quasi-two-dimensional charge order pattern on a single layer. Model calculations will be presented. Crossed stripes can also help explain a second anomaly: in ARPES of Bi2Sr2CaCu2O8+δ (Bi2212), the bilayer splitting is rapidly broadened out with underdoping. Similarly, STM studies in Bi2212 have reconstructed the Fermi surface map, but find no signs of bilayer splitting. Having crossed stripes in alternate layers does act to break up coherent bilayer splitting, particularly for fluctuating stripes. 1: T. Hanaguri, et al., Nature 430, 1001 (2004). |