High quality factor, fully switchable THz superconducting metasurface

TL;DR

This paper demonstrates a superconducting THz metasurface with a high quality factor and switchable behavior controlled by temperature, achieved through careful design and superconducting properties of Niobium.

Contribution

It introduces a fully switchable THz metasurface with a high Q factor using Niobium, highlighting the role of inductive elements and kinetic inductance in performance.

Findings

Q factor of 54 achieved

Switchable behavior controlled by temperature

Design maximizes ohmic losses and minimizes radiative coupling

Abstract

We present a complementary THz metasurface realised with Niobium thin film which displays a quality factor Q=54 and a fully switchable behaviour as a function of the temperature. The switching behaviour and the high quality factor are due to a careful design of the metasurface aimed at maximising the ohmic losses when the Nb is above the critical temperature and minimising the radiative coupling. The superconductor allows the operation of the cavity with an high Q and inductive elements with an high aspect ratio. Comparison with three dimensional finite element simulations highlights the crucial role of the inductive elements and of the kinetic inductance of the Cooper pairs in achieving the high quality factor and the high field enhancement.