Modeling two-roton bound state formation in the fractional quantum Hall system

The composite-fermion approach using extensive and parallelized numerical analysis has recently established a two-roton-bound state as the lowest energy long-wavelength neutral excitation of the fractional quantum Hall effect for a finite-particle (N similar to 30) system. By focusing on the oriented-dipole character of the magnetoroton, we model the two-roton problem and solve it variationally (analytically) to find a two-roton bound state with a, binding energy which is in good agreement with the composite fermion numerical results.