Theory of oscillations in the STM conductance resulting from subsurface defects (Review Article)

TL;DR

This review discusses recent theoretical advances in understanding how subsurface defects influence STM conductance through quantum interference, enabling defect imaging and analysis of various defect types and external magnetic field effects.

Contribution

It synthesizes recent theoretical findings on subsurface defect imaging via STM, including effects of Fermi surface anisotropy and magnetic fields, providing a comprehensive overview.

Findings

Defects can be imaged below metal surfaces using STM.

Quantum interference affects STM conductance in the presence of subsurface defects.

Magnetic fields influence conductance in defect-laden tunnel contacts.

Abstract

In this review we present recent theoretical results concerning investigations of single subsurface defects by means of a scanning tunneling microscope (STM). These investigations are based on the effect of quantum interference between the electron partial waves that are directly transmitted through the contact and the partial waves scattered by the defect. In particular, we have shown the possibility imaging the defect position below a metal surface by means of STM. Different types of subsurface defects have been discussed: point-like magnetic and non-magnetic defects, magnetic clusters in a nonmagnetic host metal, and non-magnetic defects in a s-wave superconductor. The effect of Fermi surface anisotropy has been analyzed. Also, results of investigations of the effect of a strong magnetic field to the STM conductance of a tunnel point contact in the presence of a single defect has been presented.