Thermally nonlinear metamaterial using a high-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mi>Q</mml:mi></mml:math> fluid-metal resonator

The field of nonlinear metamaterials with exciting intracoupling of multiple physics fields has recently become a topic for vital research. However, most nonlinear dynamic processes are limited to solid-state metamaterials. Here, we propose a strategy for a thermally nonlinear liquid metaresonator by designing a high-$Q$-factor reflective-type electric-$LC$ structure based on the fluid metal, mercury ($\mathrm{Hg}$). We first demonstrate that our proposed metaresonator exhibits thermally tunable properties with high temperature tuning rate. Then, the mutual couplings among the electromagnetic field, thermal field, and mechanical deformation are theoretically and numerically revealed. On this basis, the resonant frequency shift under different power levels of an incident electromagnetic wave is experimentally demonstrated to verify the thermally nonlinear properties. Our strategy for such a thermally nonlinear liquid metaresonator builds a new avenue for dynamically controlling the electromagnetic response of metamaterials.