Imaging electronic states on topological semimetals using scanning tunneling microscopy

TL;DR

This study uses scanning tunneling microscopy to investigate the electronic states of topological semimetals, revealing Dirac-like bulk bands and Fermi arc surface states, advancing understanding of their topological properties.

Contribution

It provides direct imaging and analysis of electronic states in topological semimetals, including quasiparticle interference and Landau levels, offering new insights into their surface and bulk electronic structures.

Findings

Observation of Dirac-like bulk electronic bands in semimetals.

Imaging of Fermi arc surface states and their momentum dependence.

Detection of Landau levels at high magnetic fields.

Abstract

Following the intense studies on topological insulators, significant efforts have recently been devoted to the search for gapless topological systems. These materials not only broaden the topological classification of matter but also provide a condensed matter realization of various relativistic particles and phenomena previously discussed mainly in high energy physics. Weyl semimetals host massless, chiral, low-energy excitations in the bulk electronic band structure, whereas a symmetry protected pair of Weyl fermions gives rise to massless Dirac fermions. We employed scanning tunneling microscopy/spectroscopy to explore the behavior of electronic states both on the surface and in the bulk of topological semimetal phases. By mapping the quasiparticle interference and emerging Landau levels at high magnetic field in Dirac semimetals Cd$_3$As$_2$ and Na$_3$Bi, we observed extended Dirac-like bulk electronic bands. Quasiparticle interference imaged on Weyl semimetal TaAs demonstrated the predicted momentum dependent delocalization of Fermi arc surface states in the vicinity of the surface-projected Weyl nodes.