Phase diagrams of v=2 and v=2/3 quantum Hall states in bilayer systems

We compare quantum Hall (QH) states at the Landau-level filling factor v=2 and its composite-fermion (CF) counterpart, v=2/3, in bilayer systems with various tunneling gaps. By changing the total electron density and the density difference between the two layers, we have made phase diagrams for v=2 and v =2/3. A one-particle picture provides a qualitative account of the phase diagrams, By quantitative analyses, we conclude that CF interactions exert strong influences on the fractional QH states as electron interactions do on the integer QH states. In addition, we investigate the temperature dependence of hysteresis observed at v =2/3 and find that a metastable domain structure only occurs when the magnetic field is swept upward.