  Absorption of microwave by metallic conductors is exclusively inefficient,
though being natively broadband, due to the huge impedance mismatch between
metal and free space. Reducing the thickness to ultrathin conductive film may
improve the absorbing efficiency, but is still bounded by a maximal 50% limit
induced by the field continuity. Here, we show that broadband perfect (100%)
absorption of microwave can be realized on a single layer of ultrathin
conductive film when it is illuminated coherently by two oppositely incident
beams. Such an effect of breaking the 50% limit maintains the intrinsic
broadband feature from the free carrier dissipation, and is
frequency-independent in an ultrawide spectrum, ranging typically from
kilohertz to gigahertz and exhibiting an unprecedented bandwidth close to 200%.
In particular, it occurs on extremely subwavelength scales, ~{\lambda}/10000 or
even thinner, which is the film thickness. Our work proposes a way to achieve
total electromagnetic wave absorption in a broadband spectrum of radio waves
and microwaves with a simple conductive film.
