  Mani et al. have observed [1] zero-resistance states (ZRS) and energy gaps in
a surprising setting: ultrahigh-mobility GaAs/AlGaAs heterostructures that
contain a two dimensional electron Landau system (2DELS) exhibit vanishing
diagonal resistance without Hall resistance quantization at low temperatures
and low magnetic fields when the specimen is subjected to electromagnetic wave
excitation. Zero-resistance-states occur about magnetic fields B = 4/5 Bf and B
= 4/9 Bf, where Bf = 2fm*/e, m* is the electron mass, e is the electron charge,
and f is the electromagnetic-wave frequency. Activated transport measurements
on the resistance minima also indicate an energy gap at the Fermi level. The
results suggest an unexpected radiation-induced, electronic-state-transition in
the GaAs/AlGaAs 2DELS. The authors have explained the general features of their
data as possibly arising from superconductivity through exciton exchange. Here
we show that there is another plausible mechanism based on self-organized
sliding charge density waves that does not require superconductivity to exist
in the presence of a very strong magnetic field.
