Moiré lattices formed in twisted van der Waals heterobilayers mark a new frontier in condensed matter physics. In semiconductors, such as transition metal dichalcogenides (TMDC) heterobilayers, the moiré lattice has a period on the length scale of an exciton, thereby providing a unique opportunity to create coupled exciton lattices hitherto unavailable in any other systems. In this talk I will focus on two types of heterobilayers with different band alignment. Moiré excitons are identified in both heterobilayers by investigating the optical properties engineered by the superlattices. By integrating different heterobilayers with optical cavities, moiré excitons can interact with cavity photons in weak and strong coupling regimes, respectively. Correspondingly, an interlayer exciton laser and a nonlinear moiré polariton device are demonstrated.
Long Zhang got his Ph.D. degree in optics of semiconductor microcavities under the supervision of Professor Zhanghai Chen from Fudan University in 2015. Then he joined Professor Hui Deng’s group as a postdoc at the University of Michigan. In 2020, he joined Xiamen University as an associate professor. He is interested in exploring emergent classical and quantum phenomena of semiconductor nanomaterial subjected to artificially engineered electromagnetic environment.
1 Eunice Y. Paik#, Long Zhang#, G. William Burg, Rahul Gogna, Emanuel Tutuc, and Hui Deng*. Spatially Coherent Interlayer Exciton Lasing in an Atomically-Thin Heterostructure. Nature 576 (7785), 80-84 (2019). (#: co-first authors)
2 Long Zhang, Rahul Gogna, Will Burg, Emanuel Tutuc and Hui Deng*, Photonic-Crystal Exciton-Polaritons in Monolayer Semiconductors. Nature communication, 9 (1), 713 (2018).
3 Long Zhang, Wei Xie, Xuechu Shen, Alexander Poddubny*, Yuri G. Rubo*, Boris L. Altshuler, Alexey V. Kavokin, and Zhanghai Chen*, Weak lasing in one-dimensional polariton superlattices. PNAS 112 (13), E1516–E1519 (2015).
4 Long Zhang*, Rahul Gogna, Will Burg, Jason Horng, Eunice Y. Paik, Emanuel Tutuc and Hui Deng*, High Degree of Valley-Polarization from Interlayer Excitons in van der Waals Heterostructure. Physical Review B 100, 041402(R) (2019.)