Liquid-crystal phases of quantum Hall systems

Mean-field calculations for the two-dimensional electron gas in a large mag netic field with a partially filled Landau level with index N greater than or equal to 2 consistently yield "stripe-ordered" charge-density wave groun d states, for much the same reason that frustrated phase separation leads t o stripe-ordered states in doped Mott insulators. We have studied the effec ts of quantum and thermal fluctuations about such a state and show that the y can lead to a set of electronic liquid crystalline states, particularly a stripe-nematic phase, which is stable at T>O. Recent measurements of the l ongitudinal resistivity of a set of quantum Hall devices have revealed that these systems spontaneously develop, at low temperatures, a very large ani sotropy. We interpret these experiments as evidence for a stripe nematic ph ase, and propose a general phase diagram for this system. [S0163-1829(99)06 711-9].