High-resolution Tunneling Spectroscopy of ABA-stacked Trilayer Graphene

TL;DR

This study uses high-resolution STM to explore the electronic structure of ABA-stacked trilayer graphene, revealing Landau-level crossings, effective mass changes, and unexpected LL splittings indicating novel many-body quantum Hall states.

Contribution

It provides the first detailed high-resolution spectroscopic analysis of ABA trilayer graphene, uncovering unconventional Landau level splittings and many-body effects.

Findings

Observation of Landau-level crossings between massless and massive Dirac fermions.

Detection of effective mass renormalization indicating strong electron-electron interactions.

Unconventional splittings of lowest Landau levels revealing new broken-symmetry quantum Hall states.

Abstract

ABA-stacked trilayer graphene (TLG), the simplest system consisting of both massless and massive Dirac fermions, is expected to exhibit many interesting broken-symmetry quantum Hall states and interaction-induced phenomena. However, difficulties in microscopically identifying the stacking order of the TLG and limited spectroscopic resolution have stymied experimental probes of these interesting states and phenomena in scanning tunneling microscopy (STM) studies. Here we studied the detailed features of the electronic structure in the ABA TLG by using high-resolution STM measurements. Landau-level (LL) crossings of the massless and massive Dirac fermions, and effective mass renormalization of the massive Dirac fermions were observed, indicating strong electron-electron interactions in the ABA TLG. Most unexpectedly, we observed unconventional splittings of the lowest LLs for both the massless and massive Dirac fermions in high perpendicular magnetic fields. These splittings of the LLs, which are beyond the description of tight-binding calculations, reveal unexplored broken-symmetry quantum Hall states in the ABA TLG induced by many-body effects.