Anomalous Corrugations in Scanning Tunneling Microscopy: Imaging of Individual States

Unusual corrugations observed in scanning-tunneling-microscope (STM) images of $1T-\mathrm{Ta}{\mathrm{S}}_2$, Si(111)(2×1), and graphite are explained, and are shown to be characteristic of materials where the Fermi surface has collapsed to a point at the corner of the surface Brillouin zone. This is the first clear case where the low-bias STM image is dominated by electronic structure effects rather than surface geometry. Implications for STM spatial resolution are discussed.