Kinetic inductance and voltage response dependence on temperature: Asymmetric dc SQUID case study

TL;DR

This study investigates how kinetic inductance and voltage response in asymmetric dc SQUIDs vary with temperature, device geometry, and bias current, providing insights for optimizing superconducting quantum sensors.

Contribution

It offers a combined experimental and numerical analysis of kinetic inductance effects in asymmetric SQUIDs across different temperatures and geometries, highlighting design considerations.

Findings

Kinetic inductance dominates in thin films, less sensitive to temperature in thicker films.

Voltage modulation depth decreases exponentially with total inductance.

Narrower tracks extend temperature operation range, wider tracks are more temperature-sensitive.

Abstract

Inductance plays a crucial role in the design and optimization of superconducting quantum interference devices (SQUIDs) for quantum sensing applications, since it dictates the sensitivity and coupling ratio with other circuit elements. In high-temperature superconductors the kinetic inductance, which depends on both geometry and temperature, becomes a dominant part of the device's total self-inductance, since their London penetration depth is considerably larger compared to low-temperature superconductors. In this work, we use an asymmetric SQUID to investigate the kinetic self-inductance ratio and voltage modulation depth at different operating temperatures, device geometries and bias currents. We first validate our approach by comparing our modelled data with experimental measurements. Then, through numerical simulations, we show: (i) kinetic inductance dominates for thin superconducting films, while for thicker films the inductance is less sensitive to temperature changes; (ii) the voltage modulation depth decreases exponentially with the total inductance independent of the asymmetry ratio; (iii) narrower superconducting tracks lead to a broader temperature operation range, $\Delta T \sim 30 K$, while wider tracks operate in a smaller temperature range, $\Delta T \sim 10 K$, but are more sensitive to temperature changes; and (iv) the device performance versus temperature strongly depends on the bias current used.