Title: Optically Probing Emergent Phases of Electrons in the Second Landau Level
Description: In this dissertation, I present optical emission and light scattering studies on ultraclean two-dimensional electron systems. These studies focus on emerg- ing phases in the second Landau level. I report for the excitation spectrum for fractional quantum Hall states at filling factors ν = 2+1/3, ν = 2+3/8, and ν = 2+2/5 through resonant inelastic light scattering. Resonant Rayleigh scattering is used to demonstrate that these fractional quantum Hall states are anisotropic. This work provides new insights into the nature of quasiparticle interactions of these states. It also sets the stage for the subsequent discussions about competing and coexistent phases. I present studies of emergent phases in the filling factor range 2 ≤ ν ≤ 3 using weak optical emission from the second Landau level and resonant inelas- tic light scattering by spin wave excitations. A multiplet of optical emission peaks observed that exhibit striking filling factor dependence amnifest phase competition in the second Landau level.

A correlation of emission peaks in the multiplet with anomalies observed in the spin wave spectrum uncover major impact of the spin degree of freedom on the emergent phases in the second Landau level. These experiments demonstrate the promise of optical emission from excited Landau levels as a probe of emergent phases. Results from optical emission and resonant inelastic light scattering stud- ies of the second Landau level conducted at higher temperatures (T ≈ 1 K) are also presented. Evidence that many phases observed at these higher temperatures are shown to be the same as those at lower (T ≈ 40 mK) temperatures. Striking and anomalous temperature-dependence of optical emission experiments is used to gain further insight into the nature of these competing phases.