Scanning tunneling microscopy study of the CeTe₃ charge density wave

We have studied the nature of the surface charge distribution in CeTe₃. This is a simple cleavable layered material with a robust one-dimensional incommensurate charge density wave (CDW). Scanning tunneling microscopy (STM) has been applied on the exposed surface of a cleaved single crystal. At 77 K, the STM images show both the atomic lattice of surface Te atoms arranged in a square net and the CDW modulations oriented at 45° with respect to the Te net. Fourier transform of the STM data shows Te square lattice peaks and peaks related to the CDW oriented at 45° to the lattice peaks. In addition, clear peaks are present, consistent with subsurface structure and wave-vector mixing effects. These data are supported by electronic structure calculations, which show that the subsurface signal most likely arises from a lattice of Ce atoms situated 2.53 Å below the surface Te net.