MICROSCOPIC THEORY OF LIGHT-EMISSION FROM THE SCANNING TUNNELING MICROSCOPE

A microscopic theory of light emission due to surface plasmon excitation by inelastic tunneling is developed. It is shown that the excited plasmon power spectrum function is composed of a macroscopic part and a microscopic part. The former represents the plasmon field distribution reflecting the coarse-grained shape of the tip and the surface, while the latter includes the information of the microscopic electronic states of the surface. Performing a realistic calculation by the first-principles electronic states theory, we can evaluate the intensity of the plasmon excitation. We performed a numerical study for the case of a Ag surface and a W tip, and predicted how the atomistic image can be obtained from the emission intensity. Further, we discuss the bias dependence of the excitation spectra.