Locally Incompressible Spin State of the Fractional Quantum Hall Effect when v = 3/2

Abstract

Neutral excitations in a two-dimensional electron system with an orbital and spin quantum number of 1 in the vicinity of filling factor v = 3/2 are studied experimentally. It is found that the rate of excitation relaxation to the ground state slows very strongly at v = 3/2, even though the number of vacancies in the ground state suitable for the relaxation of excitations is macroscopically large. It is shown that neutral excitations with orbital and spin quantum numbers of 1 in the state of v = 3/2 are an example of topologically protected excitation with different spin orderings in the ground and excited states. The state of v = 3/2 is an example of a locally incompressible fractional state of the quantum Hall effect, which is neither a Laughlin liquid nor an integer state of composite fermions.