Theory of microwave-assisted supercurrent in quantum point contacts

Understand

We present a microscopic theory of the effect of a microwave field on the supercurrent through a quantum point contact of arbitrary transmission.

• Our theory predicts that: (i) for low temperatures and weak fields, the supercurrent is suppressed at certain values of the superconducting phase, (ii) at strong fields, the current-phase relation is strongly modified and the current can even reverse its sign, and (iii) at finite temperatures, the microwave field can enhance the critical current of the junction.
• Apart from their fundamental interest, our findings are also important for the description of experiments that aim at the manipulation of the quantum state of atomic point contacts.