Large oscillating nonlocal voltage in multiterminal single-wall carbon nanotube devices

We report on the observation of a nonlocal voltage in a ballistic (quasi)-one-dimensional conductor, realized by a single-wall carbon nanotube with four contacts. The contacts divide the tube into three quantum dots, which we control by the back-gate voltage Vg. We measure a large oscillating nonlocal voltage Vₙₗ as a function of Vg. Though a resistor model that includes the impedance of the voltmeter can account for a nonlocal voltage including change of sign, it fails to describe the magnitude properly. The large amplitude of Vₙₗ is due to quantum interference effects and can be understood within the scattering approach of electron transport.