Abstract

The two-dimensional electron gas is a fascinating model system with an astonishingly large number of ground states. The study of this system has enriched quantum many-body physics with novel concepts such as composite fermions, topological invariants, and quasiparticles with fractional charge. The description of a small number of recently observed fractional quantum Hall states, however, may require an even more sophisticated set of concepts such as Pfaffian electronic correlations and non-Abelian statistics.

Cooling of the electrons to ultra-low temperatures has led to the discovery of new fractional states and the chance to study others in the new regime of very low densities. In this talk I will discuss how these results have shaped our understanding of both the even- and odd-denominator fractional quantum Hall states developing in the area of phase space called the second Landau level. I will also highlight new results on the exotic electronic solids forming in this region.