Zero-Field Composite Fermi Liquid in Twisted Semiconductor Bilayers.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Hall Effect

Background:

• Fractional quantum anomalous Hall (FQAH) states have been experimentally observed in semiconductor moiré superlattices like tMoTe_{2}.
• These FQAH states emerge at zero magnetic field, presenting a novel frontier in condensed matter physics.
• The composite fermion theory successfully explains phenomena in 2D electron gases under high magnetic fields.

Purpose of the Study:

• To investigate the applicability of the composite fermion framework to FQAH states in tMoTe_{2} at zero magnetic field.
• To identify and characterize novel electronic states within the tMoTe_{2} moiré superlattice system.
• To develop a theoretical model for understanding the FQAH phase diagram and predict new experimental phenomena.

Main Methods:

• Utilized exact diagonalization techniques to study the electronic properties of the tMoTe_{2} system.
• Applied the composite fermion theory to interpret the experimental observations and theoretical findings.
• Developed a long-wavelength theory for the newly identified anomalous composite Fermi liquid states.

Main Results:

• Provided exact diagonalization evidence for composite Fermi liquid states at zero magnetic field in tMoTe_{2} at fillings n=1/2 and n=3/4.
• Introduced the concept of anomalous composite Fermi liquids (ACFLs) as a key organizing principle for the FQAH phase diagram.
• The developed theory predicts a Jain sequence of FQAH states and novel commensurability oscillations.

Conclusions:

• The composite fermion description offers a powerful and unifying perspective for understanding FQAH states in tMoTe_{2} moiré superlattices.
• Anomalous composite Fermi liquids are central to the observed FQAH phenomena and the system's phase diagram.
• The theoretical predictions provide testable avenues for future experimental investigations into these quantum states.