Jiaqi Cai, Pappalardo Fellow

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Area of Physics

Condensed Matter Experiment

Research Interests

Condensed matter physicists understand the universe by tracking collective motions of elementary particles, or quasiparticles, many of which parallel elementary particles in the Standard Model. However, the principle of fractionalization uncovers quasiparticles with no Standard Model counterpart. A seminal example is the fractional quantum Hall effect (FQHE), observed in 2D electron gas subjected to an extreme magnetic field and low temperature. This effect reveals exotic quasiparticles called anyons with fractionalized charge and anyonic statistics beyond the conventional integer charge quantum number and fermion/boson dichotomy. These observations introduce the notion of topological orders. If physicists can deeply understand these topological orders, they can revolutionize quantum computing with largely reduced error rate.

Jiaqi’s research is marked by pursuit of engineering materials with topological orders, which are often characteristics of strongly correlation. A notable achievement during his Ph.D. was the discovery of fractional quantum anomalous Hall effect (FQAHE). This effect, the lattice analog of the FQHE at zero magnetic field and elevated temperature, facilitates practical research into anyonic physics. At MIT, Jiaqi is devoted to expanding the zoo of strongly correlated topological materials and uncovering exotic topological orders.

Biographical Sketch

Jiaqi grew up in Wuhan, Hubei, China and received B. S. in Applied Physics from Huazhong University of Science and Technology in the same city in 2019, where he was a theorist in condensed matter and quantum optics.

He moved to University of Washington, Seattle to pursue a Ph.D. in Physics, where he shifted his interest to condensed matter experiments and began working with Prof. Xiaodong Xu.

He was renowned for his active engagement in popularizing physical science on theChinese internet and for his Journal Club that covers a broad spectrum of physicstopics.

Selected Publications

• Cai, J.*, Anderson, E.*, Wang, C., Zhang, X., Liu, X., Holtzmann, W., … & Xu, X. Signatures of fractional quantum anomalous Hall states in twisted MoTe2. Nature, 622(7981), 63-68 (2023).
• Park, H.*, Cai, J.*, Anderson, E.*, Zhang, Y., Zhu, J., Liu, X., … & Xu, X. Observation of fractionally quantized anomalous Hall effect. Nature, 622(7981), 74-79 (2023).
• Yi, H.*, Zhao, Y. F.*, Chan, Y. T.*, Cai, J.*, Mei, R., Wu, X., … & Chang, C. Z. (2023). Interface-Induced Superconductivity in Magnetic Topological Insulator-Iron Chalcogenide Heterostructures. arXiv:2312.04353. Science (2024), in press
• Anderson, E., Fan, F. R., Cai, J., Holtzmann, W., Taniguchi, T., Watanabe, K., … & Xu, X. Programming correlated magnetic states with gate-controlled moiré geometry. Science, eadg4268 (2023).