A Composite Phononic Crystal Design for Quasiparticle Lifetime Enhancement in Kinetic Inductance Detectors

TL;DR

This paper presents a nanoscale phononic crystal filter designed to enhance quasiparticle lifetime in superconducting kinetic inductance detectors by reflecting recombination phonons, thereby improving detector performance.

Contribution

The paper introduces a novel phononic crystal design that selectively reflects quasiparticle recombination phonons, significantly increasing quasiparticle lifetime in superconducting resonators.

Findings

Achieved over 40 dB phonon transmission attenuation in simulations.

Estimated nearly two orders of magnitude increase in quasiparticle lifetime.

Designed a phononic crystal membrane with spectral gaps for high-frequency phonons.

Abstract

A nanoscale phononic crystal filter (reflector) is designed for a kinetic inductance detector where the reflection band is matched to the quasiparticle recombination phonons with the aim to increase quasiparticle lifetime in the superconducting resonator. The inductor is enclosed by a 1 um wide phononic crystal membrane section with two simple hole patterns that each contain a partial spectral gap for various high frequency phonon modes. The phononic crystal is narrow enough for low frequency thermal phonons to propagate unimpeded. With 3D phonon scattering simulations over a 40 dB attenuation in transmitted power is found for the crystal, which was previously estimated to give a lifetime enhancement of nearly two orders of magnitude.