Non-Invasive Readout of the Kinetic Inductance of Superconducting Nanostructures

TL;DR

This paper introduces a non-invasive spectroscopic method using a niobium resonator to measure the kinetic inductance of superconducting nanostructures, enabling detection of phase slips and insights into superconducting states.

Contribution

It demonstrates a novel, non-invasive technique to probe the kinetic inductance of superconducting loops, advancing understanding of phase slips and superconducting dynamics.

Findings

Resonance frequency shifts correlate with kinetic inductance changes.

The method detects phase slips in superconducting nanostructures.

Potential for studying Cooper pair density in nanostructures.

Abstract

The energy landscape of multiply connected superconducting structures is ruled by fluxoid quantization due to the implied single-valuedness of the complex wave function. The transitions and interaction between these energy states, each defined by a specific phase winding number, are governed by classical and/or quantum phase slips. Understanding these events requires the ability to probe, non-invasively, the state of the ring. Here, we employ a niobium resonator to examine the superconducting properties of an aluminum loop. By applying a magnetic field, adjusting temperature, and altering the loop's dimensions via focused ion beam milling, we correlate resonance frequency shifts with changes in the loop's kinetic inductance. This parameter is a unique indicator of the superconducting condensate's state, facilitating the detection of phase slips in nanodevices and providing insights into their dynamics. Our method presents a proof-of-principle spectroscopic technique with promising potential for investigating the Cooper pair density in inductively coupled superconducting nanostructures.