Signatures of a Novel Fermi Liquid in a Two-Dimensional Composite Particle Metal

Quasiparticle excitation gaps of the $\nu =\frac{p}{\mathrm{}(2p+1)\mathrm{}}$ fractional quantum Hall states in a low-disorder two-dimensional hole system are observed to scale linearly with $\frac{\left(\frac{e^2}{\epsilon {\ell }_B}\right)}{\mathrm{}(2p+1)\mathrm{}}$, predicted by the Chern-Simons gauge field theory if a hole-flux composite particle Fermi liquid forms around filling $\nu =\frac{1}{2}$ (${\ell }_B$ is the magnetic length). The effective mass and quantum lifetime of these new particles reveal a remarkable renormalization structure, including a strongly diverging mass and enhanced scattering close to the Fermi surface, suggesting a novel class of marginal Fermi liquid behavior.