Chiral vector determination of carbon nanotubes by observation of interference patterns near the end cap

We have observed clear interference images near the end caps of semiconducting carbon nanotubes with quasiarmchair and zigzag chiral vectors, using a scanning tunneling microscope. We performed a simple tight-binding calculation to simulate the interference patterns, in which Bloch states with k and -k wave vectors were superimposed. The calculations were able to reproduce the observed interference patterns. In addition, we demonstrated that the interference patterns can be categorized by the positions of k_{min} in the Brillouin zone that yield minimum energy in the conduction band, and can give information on the chiral vector of a carbon nanotube.