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  • Featured in Physics
  • Open Access

Candidate for a Fractional Topological Insulator in Twisted MoTe2

Yiping Wang1,2,*, Gillian E. Minarik1,*, Weijie Li3, Yves Kwan4, Shuai Yuan3, Eric Anderson3, Chaowei Hu5, Julian Ingham6, Jeongheon Choe1 et al.

Takashi Taniguchi7, Kenji Watanabe8, Xavier Roy1, Jiun-Haw Chu5, Raquel Queiroz6, James C. Hone2, N. Regnault9,10,11, Xiaodong Xu3,5, and Xiaoyang Zhu1,†

  • *These authors contributed equally to this work.
  • †Contact author: xyzhu@columbia.edu
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Phys. Rev. X 16, 031009 – Published 16 July, 2026

DOI: https://doi.org/10.1103/bvrb-z4hj

Abstract

The interplay among electronic correlation, topology, and time-reversal symmetry often leads to exotic quantum states of matter, as highlighted by the discoveries of fractional Chern insulators in twisted bilayer MoTe2(tMoTe2). Among the fractional Chern insulators (FCIs) in tMoTe2, the most robust is at a hole filling factor of ν=−23 per moiré unit cell. Here, employing pump-probe circular dichroism measurement on tMoTe2 at twist angles θ=3.9° and 3.7°, we show that a correlated state at ν=−43 exhibits an unusual Ising antiferromagnet behavior. The ν=−43 state with no net magnetization undergoes first order phase transitions at extremely low magnetic fields of |μ0H|∼2–6  mT to partially valley polarized states. This behavior is notably absent for all other correlated states in tMoTe2 and also disappears for ν=−43 at higher or lower twist angles (θ=4.0° or 3.3°). The observed magnetic signature is consistent with a theoretically proposed fractional topological insulator (FTI), consisting of two copies of ν±=−23 FCIs with opposite chirality in the K± valleys. The experimental results are supported by interacting continuum model calculations that reveal the extreme closeness in energy (ΔE<1  meV) between the putative FTI (ν±=−23 and ν∓=−23) and partially valley polarized states (ν±=−1 and ν∓=−13). Our findings present a candidate FTI with time-reversal symmetry and call for advanced transport and imaging measurements to establish the quantized helical edge modes.

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Evidence Emerges for a Fractional Topological Insulator

Published 16 July, 2026

Experiments show signs of a material that conducts electricity in opposite directions along its edges through fractionally charged quasiparticles.

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The stabilization and detection of fractional topological insulators remain elusive goals in condensed matter physics. These states require a delicate balance of time-reversal symmetry and strong electron correlations in order to host helical edge transport and fractional excitations. We addressed these challenges by applying high-sensitivity pump-probe modulation spectroscopy to investigate a twisted MoTe2 bilayer moiré superlattice at a fractional filling factor of ν=−4/3. Our measurements revealed a fragile out-of-plane antiferromagnetic response, a behavior that is atypical for moiré systems. This observation matches theoretical predictions for a fractional topological insulator composed of two fractional Chern insulators with opposite chiralities. These results also suggest the presence of an underlying pairing mechanism that could be leveraged to realize other highly correlated topological phases. Our work establishes an experimental framework for identifying fractionalized states and advances the development of platforms for topological quantum computing applications.

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Phys. Rev. X 16, 031009– Published 16 July, 2026
  • Received 26 March 2026
  • Revised 13 May 2026
  • Accepted 18 May 2026
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