  Narrow-band invisibility in an otherwise opaque medium has been achieved by
electromagnetically induced transparency (EIT) in atomic systems. The quantum
EIT behaviour can be classically mimicked by specially engineered metamaterials
via carefully controlled interference with a "dark mode". However, the narrow
transparency window limits the potential applications that require a tunable
wide-band transparent performance. Here, we present a macroscopic quantum
superconducting metamaterial with manipulative self-induced broadband
transparency due to a qualitatively novel nonlinear mechanism that is different
from conventional EIT or its classical analogs. A near complete disappearance
of resonant absorption under a range of applied rf flux is observed
experimentally and explained theoretically. The transparency comes from the
intrinsic bi-stability and can be tuned on/ off easily by altering rf and dc
magnetic fields, temperature and history. Hysteretic in situ 100% tunability of
transparency paves the way for auto-cloaking metamaterials, intensity dependent
filters, and fast-tunable power limiters.
