Evidence of a first-order phase transition between Wigner-crystal and Bubble phases of 2D electrons in higher landau levels

The detection of two resonances in the real diagonal microwave conductivity of a two-dimensional electron system (2DES) at low temperature T ≊ 35 mK, for filling factors v in the range between 4.16 and 4.28, was discussed. The resonance was attributed to Wigner-crystal and Bubbler phases of the 2DES in higher Landau levels. It was shown that for v below and above this range, only single resonances were observed. The coexistence of both phases was taken as evidence of a first-order phase transition and the transition point was estimated to be v = 4.22.