Exchange Energy Renormalization In Quantum Hall Ferromagnets With Strong Coulomb Interaction

An unusual behavior of the exchange energy scale of a quantum Hall ferromagnet with nu = 1 was found in strongly correlated two-dimensional electron systems based on MgZnO/ZnO heterostructures. The exchange contribution, entering the energy of a collective excitation, was probed by means of inelastic light scattering. It was established that, in a wide range of electron densities corresponding to the Wigner-Seitz parameter 7 < r(s) < 11, this contribution is on the order of the cyclotron energy, which is notably different from the typical scale of e(2)/epsilon l(B) that is typical for weakly interacting systems. The same trend was confirmed via numerical calculations.