Coherent control of the motion of electrons in a tunnel junction via single-cycle THz electric field

We demonstrate that single-cycle intense terahertz (THz) pulses manipulate the motion of electrons in a single tunnel junction. By tuning the carrier-envelope phase of the THz pulses, the direction of the electron tunneling through the junction was coherently controlled either from the nanotip to the sample or vice versa. By analyzing the experimental data based on the Simmons model, we found that the huge THz electric field-enhancement (~100,000) at the junction induces the dramatic modulation of the potential barrier between the nanotip and the sample on a sub-picosecond time scale.