Chiral “Graviton” and Fractional Quantum Hall Effect

We explain how the conservation laws satisfied by electrons on a single Landau level suggest that the lowest neutral excitation in a fractional quantum Hall liquid carries spin 2 or −2. We show how the spin of the magnetoroton can be determined by polarized Raman scattering. We also argue that there must be more than one magnetoroton in the Jeans sequences near ν = 1/4.