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In quantum materials, electron motion is also constrained by an emergent quantum geometry that originates from the local geometry of quantum wavefunction, which is beyond the E-k dispersion. The quantized quantum geometric effect is called topology, which leads to many interesting quantum phenomena, such as quantum spin Hall, quantum anomalous Hall, Weyl semimetals, etc. However, even without quantization, quantum geometry can also induce very interesting quantum phenomena. In this talk, I will show two interesting quantum phenomena arising from unquantized quantum geometry: the layer Hall effect and the quantum metric nonlinear Hall effect. The layer Hall effect uncovers an unusual layer-locked Berry curvature (the imaginary part of quantum geometry) which can be used to read out antiferromagnetic state. The quantum metric nonlinear Hall effect reveals the first experimental realization of the quantum metric (the real part of quantum geometry) induced anomalous Hall effect, which occurs in the second-order channel of a novel topological antiferromagnet heterostructure.
Anyuan Gao received his Ph.D. degree in physics from the Nanjing University in 2019 (advisors: Feng Miao and Baigen Wang). In Feng Miao’s research group, he focuses on the study of new quantum phenomena by engineering the band structures of 2D material heterostructures. Since then, he has been working as a postdoc in Suyang Xu’s group at Harvard University. At Harvard, he is interested in studying topology and quantum geometrical effects by designing and engineering the wavefunctions of 2D topological antiferromagnetic materials and their heterostructures using linear/nonlinear electrical transport and optical methods.
Tencent meeting link: https://meeting.tencent.com/dm/FjQAcsDcAn67 Meeting ID: 929 984 497