Shadow bands at the Fermi surface of Bi2Sr2CaCu2O8+x superconductors: structural or antiferromagnetic origin?

In this paper, we report measurements on the Fermi surface (FS) topology of Bi2Sr2CaCu2O8+x (Bi-2212) superconductors by angle scanning photoemission spectroscopy using polarized synchrotron radiation. Our k-scanning approach allows us to record the full symmetry of the main features of the FS throughout large portions of the reciprocal space, as well as their dependence on the polarization and energy of the incident light. In the recorded two-dimensional images, we have clearly identified in addition to the principal FS and its “umklapps” replicas another bands of much smaller intensity, previously reported as “shadow FS”. The k-dependence of these bands is identical that to the principal FS, but displaced by a wave-vector (π, π). In the present study, we provide a qualitative analysis of this superstructure as well as its relationship with the structural order and the low-energy magnetic fluctuations of these compounds.