Scanning Tunneling Spectroscopy Of Correlated Electronic Systems

Inhomogeneous materials

For example, high temperature superconductors:

200 x 200 angstrom topograph of Bi 2Sr 2CaCu2O8+d showing the individual Bi atoms as well as the superstructure along  the b-axis.

Map of the gap size on a 60 x 40 angstrom area.  Here we show a region where the gap is approximately  twice as large as that on the majority of the surface.

Effects of impurities on electronic structure

Scattering resonances on HTSC

Because superconductivity in HTSC is anisotropic in direction, scatterers act as strong pair breakers.  We are examining the effect on the DOS of different adatoms.

Ti adatoms on BSCCO

Measuring Off-diagonal elements of the Greens function with STM

A STM only measures the density of states for an electronic system, i.e. the diagonal elements of the Greens function. However, this is only part of the picture.  Information about the propagation of electrons and their correlations is contained in the off-diagonal elements. For this experiment, we will measure these off-diagonal elements with an STM by using impurity scatterers and analyzing the density oscillations around them.