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

Abstract

Measurements on a multilayer two-dimensional electron system (2DES) near Landau-level filling $\ensuremath{\nu}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$ reveal the disappearance of the nuclear spin contribution to the heat capacity as the ratio $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{g}$ between the Zeeman and Coulomb energies exceeds a critical value ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{g}}_{c}\ensuremath{\approx}0.04$. 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 ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{g}}_{c}$. Our experimental ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{g}}_{c}$ is smaller than the calculated ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{g}}_{c}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.054$ for an ideal 2DES. We discuss possible origins of this discrepancy.