STM studies of individual Ti impurity atoms in Sr2RuO4

The unconventional superconductor, Sr2RuO4, was studied with an ultra-low temperature scanning tunneling microscope. Atomic resolution images of the SrO plane were obtained with perturbations caused by Ti impurities substituted for 0.125% of the Ru atoms clearly visible. A complicated gap-like structure in local density of states was measured at all locations on the surface, with some modifications caused by the Ti atoms. The superconducting gap was not clearly visible, possibly due to surface termination effects, but other gap-like structures were found at ∼5 and ∼50 meV