Two-level random switching in the reentrant insulating phase around the ν=1/5 fractional quantum Hall liquid

In the insulating-phase reentrant around the ν=1/5 fractional quantum Hall liquid of a large sample, we have observed two-level random switching at a step on the nonlinear I-V curve above the conduction threshold. The I-V step separates a low-resistance region at low voltages and a high-resistance region at high voltages. The dwelling times have an exponential probability distribution and an approximately exponential dependence on voltage, but not an activated temperature dependence. The switching is not observed above ≊60 mK and for filling factor ν<0.185 when B>13 T. We suggest that, on the I-V step, the insulating phase can support two conduction configurations, corresponding to two sliding states in the Wigner-crystal picture, which switch between one another through tunneling.