3:30–4:30 pm Maria Goeppert-Mayer Lecture Hall

### Observation of Fractional Quantum Anomalous Hall Effect

#### Xiaodong Xu, University of Washington

The interplay between spontaneous symmetry breaking and topology can result in exotic quantum states of matter. A celebrated example is the quantum anomalous Hall (QAH) effect, which exhibits an integer quantum Hall effect at zero magnetic field due to topologically nontrivial bands and intrinsic magnetism. In the presence of strong electron-electron interactions, fractional-QAH (FQAH) effect at zero magnetic field can emerge, which is a lattice analog of fractional quantum Hall effect without Landau level formation. In this talk, I will present experimental observation of FQAH effect in twisted MoTe_{2 }bilayer, using combined magneto-optical [1,2], -transport [3], and scanning probe measurements [4, 5]. In addition, we find an anomalous Hall state near the filling factor -1/2, whose behavior resembles that of the composite Fermi liquid phase 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.

**Reference**

1. Signatures of Fractional Quantum Anomalous Hall States in Twisted MoTe2 Bilayer, Jiaqi Cai *et al.*, ** Nature**, https://www.nature.com/articles/s41586-023-06289-w (2023).

2. Programming Correlated Magnetic States via Gate Controlled Moiré Geometry, Eric Anderson *et al*., ** Science**, https://www.science.org/doi/full/10.1126/science.adg4268 (2023).

3. Observation of Fractionally Quantized Anomalous Hall Effect, Heonjoon Park *et al*., ** Nature**, https://www.nature.com/articles/s41586-023-06536-0 (2023).

4. Direct magnetic imaging of fractional Chern insulators in twisted MoTe2 with a superconducting sensor, Evgeny Redekop *et al.*, Accepted to ** Nature**; preprint: arXiv:2405.10269 (2024).

5. Local probe of bulk and edge states in a fractional Chern insulator, Zhurun Ji *et al.*, Accepted to ** Nature**; preprint: arXiv:2404.07157 (2024).

## Event Type

**Oct**

**17**