Strong electronic interactions, or correlations, give rise to exotic phenomena such as emergent quasiparticles, hidden quantum phases & collective dynamics. As an ultrafast spectroscopy group, we leverage light-matter interactions to study correlated motions between different degrees of freedom (spin, charge, lattice, etc.), principally in two-dimensional (2D) systems.
TWO-DIMENSIONAL MATERIALS
We use optical pump-probe spectroscopies, terahertz time-dependent spectroscopy, and two dimensional spectroscopy to study excitons and carriers in two-dimensional semiconductors, such as transition metal dichalchogenides (TMDCs), ferroelectrics, ferromagnets, and even combination of them. Of particular interest are electron-electron interaction in TMDC hetero/homobilayers, electron-phonon coupling in ferroelectrics, magnon-exciton coupling in antiferromagnets.
Phys. Rev. Lett. 2026 136 (9), 096401.
Nano Lett. 2025 (42), 15198–15205.
J. Am. Chem. Soc. 2024, 146, 14, 10052–10059
Phys. Rev. Lett. 2024, 132, 126501
Nano Lett. 2023, 23, 24, 11621–11629
Nano Lett. 2021, 21, 23, 9903–9908
Nat. Mater. 2021, 20, 1657–1662
FERRON, A NEWLY DISCOVERED QUASIPARTICLE IN 2D FERROELECTRICS
We have experimentally observed a previously theoretical collective excitation of ferroelectric order, ferrons. They exhibit intense/broadband THz emission and extremely hypersonic velocities over 105 m/s. Our discovery has opened new areas of study including integration of ferrons into 2D vdW heterostructures, ferronics for information processing, and interactions with additional quasiparticles.
Nature Materials 2025, 24, 1203-1208.
Nature Commun. 2025, 16, 1896.
CORRELATED QUANTUM PHASES + MOIRE QUANTUM MATTER
The interplay of electronic correlations and topology unlocks a wealth of exotic quantum phases in the moire platform, exemplified by the discovery of the Fractionally Quantized Anomalous Hall Effect. A significant thrust in the group aims at discovering and interrogating these quantum phases via optical pump-probe approaches, which afford extreme sensitivity to residual correlation and a time-domain perspective. Hidden disordering and recovery dynamics, often dressed by collective excitations, reflect the underlying motions that stabilize different states and provide distinct time domain signatures.
Physical Review X 2026 16 (3), 031009.
Nature Communications 2025 16 (1), 549.
Nano Letters 2024 (39), 12156–12162
Physical Review Letters 2024 132 (12), 126501.
EXCITON-COUPLED MAGNONS
Strong magnon-exciton coupling in magnetically ordered systems enables magnon precession to modulate the excitonic landscape. This interaction provides a pathway for the generation and detection of magnons using visible light, enabling their study with optical pump–probe spectroscopy. We use this technique to study magnon dynamics in vdW materials and probe how magnetic, ferroelectric, and electronic order interact in these systems.
Phys. Rev. B 2024, 109, 104401
X.Y. Zhu Group 