Sagnac interference in carbon nanotube loops

In this Letter we study electron interference in nanotube loops. The conductance as a function of the applied voltage is shown to oscillate due to interference between electron beams traversing the loop in two opposite directions, with slightly different velocities. The period of these oscillations with respect to the gate voltage, as well as the temperatures required for the effect to appear, are shown to be much larger than those of the related Fabry-Perot interference. We calculate interaction effects on the period of the oscillations, and show that even though interactions destroy much of the near degeneracy of velocities in the symmetric spin channel, the slow interference effects survive.