Probing the characteristics of carbon nanotube based devices through the Aharonov-Bohm phase

The exceptional low-dimensionality and symmetry of carbon nanotubes (CNT) are at the origin of their spectacular physical properties governed by quantum effects. Ajiki and Ando [1] predicted that an axial magnetic field would tune the bandstructure of a CNT between a metal and a semiconductor, owing to the modulation of the Aharonov-Bohm (AB) phase of the electronic wave function. This remarkable effect of magnetic field leads to a class of new physical phenomena observed in CNT. Here we report on quasimetallic CNT forming a conduction channel of three-terminal devices, which can further operate as CNT field effect transistors, under the modulation of the AB- phase. The off-state conductance varies exponentially with the magnetic flux intensity. We show that the helical symmetries of metallic CNT, as well as the characteristics of Schottky barriers formed at the metal-nanotube contacts, can be obtained by using temperature-dependent magnetoresistance measurements. [1] Ajiki, H. \& Ando, T. J. Phys. Soc. Jpn. 62, 1255-1266 (1993)