Multiparticle effects in the spectrum of collective excitations of strongly interacting two-dimensional electron systems (brief review)

Extraordinary multiparticle effects in quantizing magnetic fields that are manifested in strongly interacting two-dimensional electron systems in MgZnO/ZnO heterostructures have been reviewed. They are studied by the method of inelastic light scattering on two-dimensional systems with unique properties: strong Coulomb interaction characterized by the Wigner–Seitz parameters $r_s>5$ and a high mobility. Studies are focused on the properties of collective excitations in strong magnetic fields corresponding to the integer quantum Hall effect regime. Many results for the structure of the ground state and multiparticle contributions to the energy of collective excitations are far beyond the commonly accepted concepts of the microscopic structure of states of the quantum Hall effect in weakly interacting systems. Although any strict theory of two-dimensional electron systems at $r_s\gg1$ is absent, experimental results are adequately described by the calculations by the exact diagonalization method and the Fermi liquid model.