Heat Capacity Evidence for the Suppression of Skyrmions at Large Zeeman Energy

Measurements on a multilayer two-dimensional electron system (2DES) near Landau level filling $\nu$=1 reveal the disappearance of the nuclear spin contribution to the heat capacity as the ratio $\tilde{g}$ between the Zeeman and Coulomb energies exceeds a critical value ${\tilde{g}}_c\approx$0.04. This disappearance suggests the vanishing of the Skyrmion-mediated coupling between the lattice and the nuclear spins as the spin excitations of the 2DES make a transition from Skyrmions to single spin-flips above ${\tilde{g}}_c$. Our experimental ${\tilde{g}}_c$ is smaller than the calculated ${\tilde{g}}_c$=0.054 for an ideal 2DES; we discuss possible origins of this discrepancy.