Soft spin wave near =1: Evidence for a magnetic instability in skyrmion systems

The ground state of the two-dimensional electron gas near =1 is investigated by inelastic light scattering measurements carried down to very low temperatures. Away from =1, the ferromagnetic spin wave collapses and a new low-energy spin wave emerges below the Zeeman gap. The emergent spin wave shows soft behavior as its energy increases with temperature and reaches the Zeeman energy for temperatures above 2K. The observed softening indicates an instability of the two-dimensional electron gas towards a magnetic order that breaks spin rotational symmetry. We discuss our findings in light of the possible existence of a Skyrme crystal.