Imaging the symmetry breaking of molecular orbitals in carbon nanotubes

Hong Lin (1) , Jérôme Lagoute (1) , Vincent Repain (1) , Cyril Chacon (1) , Yann Girard (1) , François Ducastelle (2) , Hakim Amara (2) , Annick Loiseau (2) , Patrick Hermet (3) , Luc Henrard (3) , Sylvie Rousset (1)

1 MPQ (UMR_7162) - Laboratoire Matériaux et Phénomènes Quantiques
2 LEM - ONERA - CNRS - Laboratoire d'étude des microstructures [Châtillon]
3 PMR - Centre de Recherche en Physique de la Matière et du Rayonnement [Namur]

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 π orbitals confirmed by ab initio calculations, perfectly reproduces the experimental results.

Mots clés: Carbon nanotubes; Scanning Tunneling Spectroscopy; Wave functions

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Hong Lin, Jérôme Lagoute, Vincent Repain, Cyril Chacon, Yann Girard, et al.. Imaging the symmetry breaking of molecular orbitals in carbon nanotubes. 2009. ⟨hal-00435099⟩