Photogalvanic effects in heteropolar nanotubes

We show that an electrical shift current is generated when electrons are ph otoexcited from the valence to conduction bands on a BN nanotube. This phot ocurrent follows the light pulse envelope and its symmetry is controlled by the atomic structure of the nanotube. We find that the shift current has a n intrinsic quantum mechanical signature in which the chiral index of the t ube determines the direction of the current along the tube axis. We identif y the discrete lattice effects in the tangent plane of the tube that lead t o an azimuthal component of the shift current. The nanotube shift current c an lend to ultrafast optoelectronic and optomechanical applications.