Dissemin is shutting down on January 1st, 2025

Published in

arXiv, 2023

DOI: 10.48550/arxiv.2308.02657

Nature Research, Nature, 7981(622), p. 74-79, 2023

DOI: 10.1038/s41586-023-06536-0

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Observation of fractionally quantized anomalous Hall effect

This paper was not found in any repository, but could be made available legally by the author.
This paper was not found in any repository, but could be made available legally by the author.

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Abstract

The integer quantum anomalous Hall (QAH) effect is a lattice analog of the quantum Hall effect at zero magnetic field. This striking transport phenomenon occurs in electronic systems with topologically nontrivial bands and spontaneous time-reversal symmetry breaking. Discovery of its putative fractional counterpart in the presence of strong electron correlations, i.e., the fractional quantum anomalous Hall (FQAH) effect, would open a new chapter in condensed matter physics. Here, we report the direct observation of both integer and fractional QAH effects in electrical measurements on twisted bilayer MoTe$_2$. At zero magnetic field, near filling factor $ν= -1$ (one hole per moiré unit cell) we see an extended integer QAH plateau in the Hall resistance $R_\text{xy}$ that is quantized to $h/e^2 ± 0.1 \%$ while the longitudinal resistance $R_\text{xx}$ vanishes. Remarkably, at $ν=-2/3$ and $-3/5$ we see plateau features in $R_\text{xy}$ at $3h/2e^2 ± 1\%$ and $5h/3e^2 ± 3\%$, respectively, while $R_\text{xx}$ remains small. All these features shift linearly in an applied magnetic field with slopes matching the corresponding Chern numbers $-1$, $-2/3$, and $-3/5$, precisely as expected for integer and fractional QAH states. In addition, at zero magnetic field, $R_\text{xy}$ is approximately $2h/e^2$ near half filling ($ν= -1/2$) and varies linearly as $ν$ is tuned. This behavior resembles that of the composite Fermi liquid in the half-filled lowest Landau level of a two-dimensional electron gas at high magnetic field. Direct observation of the FQAH and associated effects paves the way for researching charge fractionalization and anyonic statistics at zero magnetic field.