Quasi-Hole Structures in the Electron-Removal Spectrum of Fractional Quantum Hall Systems

The electron-removal spectrum in a fractional quantum Hall (FQH) droplet with a Landau level filling l/p (p: odd integer) is derived numerically. The spectrum of a small-sized droplet as a function of the removed angular momentum shows a p-fold iterative structure at the lower threshold. The structure is due to quasi-holes, and is analogous to the twice refrained spinon thresholds in the dynamical structure factor of the Heisenberg chain. It is discussed that the iterative structure should remain in the FQH droplet with a large number of electrons.