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 (g) over tilde between the Zeeman and Coulomb energies exceeds a critical value (g) over tilde(c) approximate to 0.04. This disappearance suggests the vanishing of the Skyrmion-mediated coupling between the lattice and the nuclear spills as the spin excitations of the 2DES make a transition from Skyrmions to single spin flips; above (g) over tilde(c). Our experimental g, is smaller than the calculated (g) over tilde(c) = 0.054 for an ideal 2DES. We discuss possible origins of this discrepancy. [S0031-9007(99)08835-3].