EXCITONIC INSTABILITY AND TERMINATION OF FRACTIONAL QUANTUM HALL-EFFECT

A shortcoming of the theoretical descriptions of the fractional quantu m Hall effect (FQHE) has been that they do not tell us when FQHE will not occur. In particular, they do not produce any instabilities at sma ll filling factors, where the actual ground state is not a FQHE liquid but a Wigner solid. We show in this paper that building excitations i n terms of composite fermions, a neutral excitation of the Laughlin st ate at 1/9 has lower energy than the Laughlin state itself, indicating an absence of FQHE at v less than or equal to 1/9.