Developing Fractional Quantum Hall States at Even-Denominator Fillings 1/6 and 1/8

Area of Science:

• Condensed Matter Physics
• Quantum Hall Effect
• Many-Body Physics

Background:

• In low-disorder 2D electron systems, electron-electron interactions create exotic phases in the extreme quantum limit (ν<1).
• Even-denominator states (e.g., ν=1/2, 1/4) are typically composite fermion Fermi seas, while odd-denominator states are Jain fractional quantum Hall states (FQHSs).
• Insulating behavior is observed below ν=1/5, often attributed to pinned Wigner crystals.

Purpose of the Study:

• To investigate the emergence of fractional quantum Hall states (FQHSs) at novel even-denominator fillings in ultra-high-quality GaAs systems.
• To explore the nature of these states and their potential implications for exotic particle excitations.

Main Methods:

• Experimental measurements on ultra-high-quality, dilute GaAs two-dimensional electron systems.
• Analysis of magnetoresistance minima superimposed on an insulating background at low Landau level filling factors (ν<1).

Main Results:

• Developing FQHSs were observed at ν=p/(6p±1) and ν=p/(8p±1), indicated by magnetoresistance minima.
• A pronounced minimum at ν=1/6 and a weaker one at ν=1/8 were detected, contrasting with behavior at ν=1/2 and 1/4.
• These findings suggest FQHSs at even denominators 1/6 and 1/8, possibly stabilized by composite fermion pairing.

Conclusions:

• Ultra-high-quality samples exhibit unexpected fractional quantum Hall states (FQHSs) at even-denominator fillings 1/6 and 1/8.
• These newly observed states are likely stabilized by the pairing of composite fermions carrying six and eight flux quanta.
• The discovered FQHSs may harbor non-Abelian anyon excitations, opening new avenues for research.