Imaging the symmetry breaking of molecular orbitals in carbon nanotubes

TL;DR

This study provides the first detailed experimental visualization of symmetry breaking in molecular orbitals of carbon nanotubes, revealing bond asymmetries and orbital interference patterns using advanced spectroscopy and modeling.

Contribution

It introduces a comprehensive experimental approach to imaging molecular orbitals in nanotubes and confirms findings with theoretical models, advancing understanding of their electronic properties.

Findings

Observation of bond asymmetry at Van Hove singularities

Identification of two types of complementary orbitals

Validation of tight-binding model with ab initio calculations

Abstract

Carbon nanotubes have attracted considerable interest for their unique electronic properties. They are fascinating candidates for fundamental studies of one dimensional materials as well as for future molecular electronics applications. The molecular orbitals of nanotubes are of particular importance as they govern the transport properties and the chemical reactivity of the system. Here we show for the first time a complete experimental investigation of molecular orbitals of single wall carbon nanotubes using atomically resolved scanning tunneling spectroscopy. Local conductance measurements show spectacular carbon-carbon bond asymmetry at the Van Hove singularities for both semiconducting and metallic tubes, demonstrating the symmetry breaking of molecular orbitals in nanotubes. Whatever the tube, only two types of complementary orbitals are alternatively observed. An analytical tight-binding model describing the interference patterns of ? orbitals confirmed by ab initio calculations, perfectly reproduces the experimental results.