Tilt-induced phase transitions in even-denominator fractional quantum Hall states at the ZnO interface

Abstract

Strongly interacting electrons in a ZnO quantum well reveal intriguing electronic properties that were not observed in traditional semiconductor systems, such as in a GaAs heterojunction. In a tilted magnetic field, the even-denominator fractional quantum Hall states in this system exhibit unique phase transitions that necessitate a proper understanding. Since here the Landau level gap is very small, it is essential to consider a screened Coulomb potential in order to include the effects of all Landau levels. We observe an incompressible state--compressible state phase transition induced by the tilted field with different properties for the $\frac{3}{2}$ and $\frac{7}{2}$ filling factors. Additionally, the disappearance of the $\frac{5}{2}$ state in the experiment is most likely due to the presence of a screened Coulomb potential. We, however, propose that a wider quantum well may help to stabilize the incompressible phase of the $\frac{5}{2}$ filling factor, and thereby make the fractional quantum Hall effect observable in this state.