Detection of ultrafast oscillations in Superconducting Point-Contacts by means of Supercurrent Measurements

TL;DR

This paper models how mechanical oscillations influence supercurrent in superconducting point contacts, revealing sharp current dips that encode the oscillator's frequency and coupling, aiding nanomechanical resonator design.

Contribution

It introduces a microscopic non-equilibrium Green function approach to analyze supercurrent modulation by mechanical oscillations in superconducting contacts.

Findings

Current dips reveal oscillator frequency and coupling strength.

Analytical expressions for dip position and width derived from a two-level model.

Relevance for designing superconducting nanomechanical resonators.

Abstract

We present a microscopic calculation of the nondissipative current through a superconducting quantum point contact coupled to a mechanical oscillator. Using the non-equilibrium Keldysh Green function approach, we determine the current-phase relation. The latter shows that at certain phases, the current is sharply suppressed. These dips in the current-phase relation provide information about the oscillating frequency and coupling strength of the mechanical oscillator. We also present an effective two-level model from which we obtain analytical expressions describing the position and width of the dips. Our findings are of relevance for nanomechanical resonators based on superconducting materials.