Crossover and Coexistence of Quasiparticle Excitations in the Fractional Quantum Hall Regime at $ν\leq 1/3$

C. F. Hirjibehedin, A. Pinczuk, B. S. Dennis, L. N. Pfeiffer, K. W. West

Published 2003-06-05Version 1

New low-lying excitations are observed by inelastic light scattering at filling factors $\nu=p/(\phi p \pm 1)$ of the fractional quantum Hall regime with $\phi=4$. Coexisting with these modes throughout the range $\nu \leq 1/3$ are $\phi=2$ excitations seen at 1/3. Both $\phi=2$ and $\phi=4$ excitations have distinct behaviors with temperature and filling factor. The abrupt first appearance of the new modes in the low energy excitation spectrum at $\nu \lesssim 1/3$ suggests a marked change in the quantum ground state on crossing the $\phi=2 \to \phi=4$ boundary at $\nu = 1/3$.