Photophysics, Excitons, Quantum Materials, Ultrafast Spectroscopy
Summary: We are interested in photo-physics in nano, molecular, and hybrid semiconductors and interfaces. We focus on dynamics of quasiparticles (excitons, polarons, polaritons, etc.) and their many-body interactions. These interactions are important to a range of optoelectronic processes, such as solar energy conversion, light emission, and polariton condensation. We employ state-of-the-art experimental techniques, including, among others, time-resolved photoemission spectroscopy, femtosecond nonlinear optical spectroscopies, transient absorption and emission spectroscopies, and two-dimensional spectroscopies. As examples, recent discoveries in our lab revealed how dynamic screening and large polaron formation can make lead halide perovskite defect tolerant, how excitons at van der Waals 2D semiconductor interfaces undergo phase transitions, and how magnetic order couple to excitons in 2D magnetic semiconductors. Our group is part of the DOE Energy Frontier Research Center (EFRC) on Programmable Quantum Materials and part of the NSF Materials Research Science and Engineering Center (MRSEC) for Precision-Assembled Quantum Materials.
Youn Jue Bae, Jue Wang, Allen Scheie, Junwen Xu, Daniel G. Chica, Geoffrey M. Diederich, John Cenker, Michael E. Ziebel, Yusong Bai, Haowen Ren, Cory R. Dean, Milan Delor, Xiaodong Xu, Xavier Roy, Andrew D. Kent, X.-Y. Zhu, “Exciton-Coupled Coherent Magnons in a 2D Semiconductor,” Nature 2022, 609, 282-286
Nathan P. Wilson, Kihong Lee, John Cenker, Kaichen Xie, Avalon H. Dismukes, Evan J. Telford, Jordan Fonseca, Shivesh Sivakumar, Cory Dean, Ting Cao, Xavier Roy, Xiaodong Xu, X.-Y. Zhu, “Interlayer electronic coupling on demand in a 2D Magnetic Semiconductor,” Nature Mater. 2021, 20, 1657-1663.
Fang Liu, Wenjing Wu, Yusong Bai, Sang Hoon Chae, Qiuyang Li, Jue Wang, James Hone, X.-Y. Zhu, “Disassembling 2D van der Waals Crystals into Macroscopic Monolayers and Reassembling into Artificial Lattices,” Science 2020, 367, 903-906.
Yusong Bai, Lin Zhou, Jue Wang, Wenjing Wu, Leo McGilly, Dorri Halbertal, Chiu Fan B. Lo, Fang Liu, Jenny Ardelean, Pasqual Rivera, Nathan R. Finney, Xuchen Yang, Dmitri N. Basov, Wang Yao, Xiaodong Xu, James Hone, Abhay Pasupathy, X.-Y. Zhu, “Excitons in strain-induced one-dimensional moiré potentials at transition-metal dichalcogenide heterojunctions,” Nature Mater. 2020, 19, 1068-1073.
Kiyoshi Miyata, X.-Y. Zhu, “Ferroelectric large polarons,” Nature Mater. 2018, 17, 379-381.
Nicholas R. Monahan, Dezheng Sun, H. Tamura, Kristopher W. Williams, Bolei Xu, Yu Zhong, Bharat Kumar, Colin Nuckolls, Avetik R. Harutyunyan, Gugang Chen, Hai-Lung Dai, D. Beljonne, Yi Rao, X.-Y. Zhu, “Dynamics of the triplet pair state reveals the likely co-existence of coherent and incoherent singlet fission in crystalline hexacene,” Nature Chem. 2017, 9, 341-346.
Haiming Zhu, Kiyoshi Miyata, Yongping Fu, Jue Wang, Prakriti P. Joshi, Daniel Niesner, Kristopher J. Williams, Song Jin, X.-Y. Zhu, “Screening in crystalline liquids protects energetic carriers in hybrid perovskites,” Science, 2016, 353, 1409-1413.
Haiming Zhu, Yongping Fu, Fei Meng, Xiaoxi Wu, Zizhou Gong, Qi Ding, Martin V. Gustafsson, M. Tuan Trinh, Song Jin, X.-Y. Zhu, “Lead halide perovskite nanowire lasers with low lasing thresholds and high quality factors,” Nature Mater. 2015, 14, 636-642.