Abstract
Interactions between the constituents of a condensed matter system can drive it through a plethora of different phases due to many-body effects. A prominent platform for it is a dilute two-dimensional electron system in a magnetic field, which evolves intricately through various gaseous, liquid and solid phases governed by Coulomb interaction. Here we report on the experimental observation of a phase transition between the composite fermion liquid and adjacent magnetic field induced phase with a character of Wigner solid. The experiments are performed in the lowest Landau level of a MgZnO/ZnO two-dimensional electron system with attributes of both a liquid and a solid. An in-plane magnetic field component applied on top of the perpendicular magnetic field extends the Wigner-like phase further into the composite fermion liquid phase region. Our observations indicate the direct competition between a composite fermion liquid and a Wigner solid formed either by electrons or composite fermions.
Highlights
Interactions between the constituents of a condensed matter system can drive it through a plethora of different phases due to many-body effects
Being in the lowest Landau level (LL) the electron system experiences competition between the composite fermion liquid phase and the magnetic field induced Wigner solid phase, which manifests as a large magnetoresistance peak around or below ν = 1/34,6
We study the magnetotransport in a ZnO heterostructure in the magnetic field region between the composite fermions (CF) liquid phase formed at ν = 1/2 and the high resistivity phase appearing at higher field and exhibiting attributes of a Wigner solid[25,26]
Summary
Interactions between the constituents of a condensed matter system can drive it through a plethora of different phases due to many-body effects. When the electrons occupy half of available states in the lowest LL, e.g., filling factor ν = 1/2, the electrons prefer to reduce their interaction by virtue of capturing two magnetic flux quanta resulting in the emergence of new particles, called composite fermions (CF)[2,3] These particles form a Fermi surface at ν = 1/2 and move in an effective field Beff = B − Bν = 1/2 (Fig. 1, middle panel) giving rise to magnetoresistance oscillations. Being in the lowest Landau level (LL) the electron system experiences competition between the composite fermion liquid phase and the magnetic field induced Wigner solid phase, which manifests as a large magnetoresistance peak around or below ν = 1/34,6. Owning to a simple band structure of ZnO as compared to p-type GaAs, this oxide material is an attractive platform to access the competition between liquid and solid phases in the fractional quantum Hall regime
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