Electron correlation in the second Landau level; a competition between   many, nearly degenerate quantum phases
  At a very low temperature of 9mK, electrons in the 2nd Landau level of an extremely high mobility two-dimensional electron system exhibit a very complex electronic behavior. With varying filling factor, quantum liquids of different origins compete with several insulating phases leading to an irregular pattern in the transport parameters. We observe a fully developed $\nu=2+2/5$ state separated from the even-denominator $\nu=2+1/2$ state by an insulating phase and a $\nu=2+2/7$ and $\nu=2+1/5$ state surrounded by such phases. A developing plateau at $\nu=2+3/8$ points to the existence of other even-denominator states. 
J.S. Xia, W. Pan, C.L. Vincente, E.D. Adams, N.S. Sullivan, H.L.   Stormer, D.C. Tsui, L.N. Pfeiffer, K.W. Baldwin, and K.W....