Energy gap in tunneling spectroscopy: effect of the chemical potential shift

TL;DR

This paper investigates how shifts in the chemical potential affect tunneling conductance spectra in gapped systems, revealing significant distortions and deriving correction expressions that depend on the chemical potential position.

Contribution

It provides a new analytical expression for the correction to tunneling conductance due to chemical potential shifts, highlighting their impact on spectral features.

Findings

Chemical potential shifts cause notable distortions in $dI/dV$ spectra.

The correction depends on the chemical potential position relative to the gap.

Correction magnitude varies linearly with tip-sample separation $z$.

Abstract

We study the effect of a shift of the chemical potential level on the tunneling conductance spectra. In the systems with gapped energy spectra, significant chemical-potential dependent distortions of the differential tunneling conductance curves, $dI/dV$, arise in the gap region. An expression is derived for the correction of the $dI/dV$, which in a number of cases was found to be large. The sign of the correction depends on the chemical potential level position with respect to the gap. The correction of the $dI/dV$ associated with the chemical potential shift has a nearly linear dependence on the tip-sample separation $z$ and vanishes at $z\to 0$.