Observation of the local density-of-states modulation in Bi2Sr1.6Gd0.4CuO6+δ by scanning tunneling microscopy

We performed scanning tunneling microscopy measurements in the pseudogap state and the superconducting state in optimally doped Bi2Sr1.6Gd0.4CuO6+δ. The electronic states showed two-dimensional local density-of-states (LDOS) modulation above and below Tc. In both of the states, the modulation period did not show the energy dispersion in our experimental accuracy, and was about five lattice constants. This indicates that the modulations observed above and below Tc are the same entity.