Depinning transition of bubble phases in a high Landau level

In the higher Landau levels (N>0) a reentrant integer quantum Hall effect (RIQHE) state, which resides at fractional filling factors but exhibits integer Hall plateaus, has been previously observed and studied extensively. The nonlinear dynamics of the RIQHE were measured by microwave resonance, with the results consistent with an electronic bubble phase pinned by impurities. We have carried out depinning experiments on the N=2 bubble phases by using Corbino geometry, where depinning threshold values have been systematically measured as a function of magnetic fields and temperatures. Domain sizes and pinning potential of the bubble phases have been estimated from the nonlinear transport data.