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Observation of fractionally quantized anomalous Hall effect
Heonjoon Park1, Jiaqi Cai1, Eric Anderson1
1Department of Physics, University of Washington, Seattle, WA, USA.
Nature
|August 17, 2023
Summary
Researchers observed both integer and fractional quantum anomalous Hall (QAH) effects in twisted bilayer MoTe2. This discovery enables new research into fractionalization and anyonic statistics at zero magnetic field.
Area of Science:
- Condensed Matter Physics
- Materials Science
Background:
- The quantum anomalous Hall (QAH) effect is a zero-magnetic-field analogue of the quantum Hall effect, occurring in topologically non-trivial band systems with broken time-reversal symmetry.
- The discovery of a fractional QAH effect, driven by electron correlations, would represent a significant advancement in condensed matter physics.
Purpose of the Study:
- To report the direct observation of both integer and fractional QAH effects.
- To investigate these phenomena in twisted bilayer MoTe2 at zero magnetic field.
Main Methods:
- Electrical transport measurements on twisted bilayer MoTe2.
- Analysis of Hall resistance (Rxy) and longitudinal resistance (Rxx) at various filling factors (ν).
- Investigation of the magnetic field dependence of observed features.
Main Results:
- Observation of an integer QAH plateau at ν = -1, with Rxy quantized to h/e² and vanishing Rxx.
- Observation of fractional QAH plateau features at ν = -2/3 and -3/5.
- Linear shift of all features with applied magnetic field, consistent with Chern numbers -1, -2/3, and -3/5.
- Resemblance to composite Fermi liquid behavior near half-filling (ν = -1/2).
Conclusions:
- Direct observation of integer and fractional QAH effects in twisted bilayer MoTe2 at zero magnetic field.
- This provides a platform for studying charge fractionalization and anyonic statistics without external magnetic fields.
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