Phase Transition in theν=2Bilayer Quantum Hall State

Abstract

The width of the Hall plateau and the activation energy were measured in the bilayer quantum Hall state at filling factors $\nu =2\mathrm{}$, 1, and 2/3 by changing the total electron density and the density ratio in the two quantum wells. Their behaviors are remarkably different. The $\nu =1\mathrm{}$ state is found to be stable over all measured range of the density difference. The $\nu =2\mathrm{}/3$ state is stable only around the balanced point. The $\nu =2\mathrm{}$ state shows a phase transition between these two types of states as the electron density is changed.