Collapse of minibands in far-infrared irradiated superlattices

Quasienergy minibands in superlattices which interact with intense far-infrared laser radiation collapse under conditions that are experimentally accessible. In particular, it is shown that the miniband width becomes close to, but not identical to, zero if the ratio of the Bloch frequency and the laser frequency approaches a zero of the Bessel function ${\mathit{J}}_0$.