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Confinement-Induced Chiral Edge Channel Interaction in Quantum Anomalous Hall Insulators
Ling-Jie Zhou1, Ruobing Mei1, Yi-Fan Zhao1
1Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Physical Review Letters
|March 10, 2023
Summary
Quantum anomalous Hall insulators feature chiral edge channels (CECs) for zero-resistance transport. This study reveals CECs decay rapidly, with deviations in narrow samples caused by disorder-induced bulk states interacting with CECs.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Phenomena
Background:
- Quantum anomalous Hall (QAH) insulators exhibit insulating bulk with conducting chiral edge channels (CECs).
- CECs are theoretically predicted to be confined to 1D edges and decay exponentially into the 2D bulk.
Purpose of the Study:
- Investigate the spatial extent and behavior of CECs in QAH insulators.
- Determine the factors causing deviations from quantized Hall resistance in narrow QAH devices.
Main Methods:
- Fabrication and characterization of QAH devices in a Hall bar geometry with varying widths.
- Application of gate voltages to tune device properties.
- Experimental measurement of Hall resistance.
- Theoretical modeling of CEC wave function decay and disorder effects.
Main Results:
- QAH effect observed in devices as narrow as ~72 nm, indicating intrinsic CEC decay length < ~36 nm.
- Hall resistance deviates from quantized values in samples < 1 μm in the electron-doped regime.
- Theoretical calculations show exponential decay followed by a long tail in CEC wave functions due to disorder-induced bulk states.
Conclusions:
- The deviation from quantized Hall resistance in narrow QAH samples is attributed to the interaction between opposite CECs.
- This interaction is mediated by disorder-induced bulk states within the QAH insulator.
- Experimental observations are consistent with theoretical predictions regarding CEC behavior and disorder effects.
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