Quasiholes in a MgZnO/ZnO heterojunction as vacancions

Recombination of two-dimensional electrons of a low density in a MgZnO/ZnO heterojunction with localized valence-band holes is considered. It is suggested that quasiholes appearing in the process of photoluminescence of strongly interacting two-dimensional electrons should be considered as vacancion quasiparticles in a quantum Wigner crystal. Vacancions formed upon the removal of an electron from the crystal are delocalized owing to the tunneling effect. The vacancion energies $E(k)$ form a band of width $D$ that depends on the probability of vacancy tunneling. The width $D$ corresponds to the width of the photoluminescence band of the two-dimensional electron system. The shape of the photoluminescence band of the Wigner crystal is obtained using the tight-binding approximation for the vacancion dispersion relation $E(k)$ is compared with experimental results.