Analytic wave functions for neutral bulk excitations in fractional quantum Hall fluids

Abstract

We show the model wave functions for the neutral collective modes in fractional quantum Hall (FQH) states have simple analytic forms obtained from judicially reducing the powers of selected pairs in the ground state Jastrow factor. This scheme of ``pair excitations''works for the magnetoroton modes of single-component Abelian and non-Abelian FQH states, as well as the neutral fermion mode for the Moore-Read state. The analytic wave functions allow us to compute the ``quadrupole gap'' of the magnetoroton mode in the thermodynamic limit, which was previously inaccessible to the numerics. The quadrupole gap is related to the fusion of the charges in the two-dimensional plasma picture, extending the plasma analogy to neutral excitations. A lattice diagrammatic method of representing these many-body wave functions and FQH elementary excitations is also presented.