The effect of Zeeman energy on heat capacity of GaAs/AlGaAs heterostructures near nu = 1.

By controlling the ratio eta between the Zeeman and Coulomb energies, the heat capacity of a multilayer two-dimensional electron system (2DES) is measured near Landau level filing v = 1 at 60 mK. The data reveal the disappearance of the nuclear spin contribution of GaAs quantum wells to the heat capacity as eta exceeds a critical value eta(c) approximate to 0.03. This result is interpreted as the effect of the transition from Skyrmions to single electron spin flips at large Zeeman energy. (C) 2000 Elsevier Science B.V. All rights reserved.