Half-Quantized Chiral Edge Current in a C=1/2 Parity Anomaly State.

Area of Science:

• Condensed Matter Physics
• Quantum Field Theory
• Materials Science

Background:

• The C=1/2 parity anomaly state in quantum field theory predicts a half-quantized Hall conductance.
• Previous studies in semimagnetic topological insulator (TI) bilayers showed signatures of this state, but direct evidence of half-quantized chiral edge currents was missing.

Purpose of the Study:

• To experimentally observe and confirm the existence of a half-quantized chiral edge current.
• To establish asymmetric magnetic TI trilayers as a platform for studying the C=1/2 parity anomaly state and single Dirac fermion physics.

Main Methods:

• Fabrication of asymmetric magnetic TI trilayers using molecular beam epitaxy.
• Transport measurements under specific in-plane magnetic field regimes.
• Numerical simulations to analyze the transport properties and edge channel behavior.

Main Results:

• Observation of a robust half-quantized Hall conductance plateau in the asymmetric magnetic TI trilayer.
• Enhanced nonlocal and nonreciprocal transport signals, indicating a half-quantized chiral edge current.
• Numerical simulations confirmed the half-quantized chiral edge channel as the carrier of the observed conductance plateau.

Conclusions:

• Experimental evidence for half-quantized chiral edge transport in a C=1/2 parity anomaly state has been demonstrated.
• The observed phenomenon arises from massless Dirac electrons and differs from the C=1 quantum anomalous Hall state.
• Asymmetric magnetic TI trilayers serve as a promising platform for exploring topological magnetoelectric effects and quantized magneto-optical responses.