  We propose to use logarithmic spiral resonators for efficient absorption of
microwaves. By combining their scale invariant geometries and Fabry-Perot-type
resonances stemming from the fundamental TM mode, we realize a microwave
metasurface with broadband absorption performance. The metasurface comprises
logarithmic spiral resonators backed with a metallic surface and it can absorb
>95% of incident microwave energy within the frequency range of 6 GHz - 37 GHz.
We discuss the physics underlying the broadband absorption and the crucial role
of vortex energy flow. The study opens a new direction of electromagnetic wave
absorption by employing the scale invariance of Maxwell equations.
