Inelastic Electron Tunneling Spectroscopy for Topological Insulators

TL;DR

This paper investigates how inelastic scattering affects the surface states of topological insulators using IETS, revealing spectral modifications, resonance phenomena, and potential quantum phase transitions.

Contribution

It provides a detailed analysis of inelastic scattering effects on Dirac surface states in TIs, including spectral changes and the emergence of resonance peaks across coupling regimes.

Findings

Inelastic scattering significantly alters Dirac surface states.

Resonance peaks appear at intermediate coupling.

Evidence suggests a possible local quantum phase transition.

Abstract

Inelastic Electron Tuneling Spectroscopy (IETS) is a powerful spectroscopy that allows one to investigate the nature of local excitations and energy transfer in the system of interest. We study IETS for Topological Insulators (TI) and investigate the role of inelastic scattering on the Dirac node states on the surface of TIs. Local inelastic scattering is shown to significantly modify the Dirac node spectrum. In the weak coupling limit, peaks and steps are induced in second derivative $d^2I/dV^2$. In the strong coupling limit, the local negative U centers are formed at impurity sites, and the Dirac cone structure is fully destroyed locally. At intermediate coupling resonance peaks emerge. We map out the evolution of the resonance peaks from weak to strong coupling, which interpolate nicely between the two limits. There is a sudden qualitative change of behavior at intermediate coupling, indicating the possible existence of a local quantum phase transition. We also find that even for a simple local phonon mode the inherent coupling of spin and orbital degrees in TI leads to the spin polarized texture in inelastic Friedel oscillations induced by local mode.