Charge modulation driven Fermi surface of Pb–Bi2201

It is well known that the (1×5) superstructure of Bi cuprate superconductors will be suppressed due to doping with Pb. Nevertheless, a Fermi surface map of Bi2−yPbySr2−xLaxCuO6+δ ( y = 0.4 and x = 0.4 ) determined by angular resolved photoemission (ARPES) revealed additional Fermi surface features. Low-energy electron diffraction (LEED) and X-ray diffraction of this sample showed no sign of any superstructure. Scanning tunneling microscopy (STM), on the other hand, revealed two distinct modulations of the charge density, one of (1×32) and a second of (6×6) periodicity. The wave vectors of both modulations have been extracted and used to simulate the corresponding Fermi surface, which is compared with the experimental one. The origin of these modulations is discussed in terms of dopant ordering.