LCAO Tight-Binding Calculation of the LDOS and The STM Image
The local density of states at the tip position in an STM experiment, which according to a simple perturbation treatment is approximately proportional to the tunneling current, is developed in the framework of the LCAO tight-binding theory. This clearly shows two important contributions to the local density of states. The surface atomic geometry plays a predominant role due to the exponential decay of atomic orbitals The second contribution comes from the nature of the electronic wavefunctions determined for the bulk crystal, specifically the atomic orbital populations, near the Fermi level. It may happen that the second factor will prevail over the first factor, but only under extreme conditions. The case of WTe2, where a recent STM experiment suggested the observation of the subsurface metal layer instead of the surface nonmetal layer, is calculated in this work. The result excludes any observation of the subsurface layer of this sample, and it rather points towards surface reconstruction as a possible explanation of the STM image.
KeywordsFermi Level Scanning Tunneling Microscopy Atomic Orbital Tunneling Current Scanning Tunneling Microscopy Image
Unable to display preview. Download preview PDF.