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Research interest: Light-matter interaction & quantum physics in nanomaterial devices
Femtosecond laser technique
Nanomaterial device fabrication
Quantum state optoelectronics
Exciton-mediated light-matter interaction across atomic layers
Exciton-mediated light-matter interaction across atomic layers
Coulomb interactions in layered transition metal dichalcogenides (TMDs) give rise to a rich landscape of correlated electronic phenomena, including Wigner crystallization, Mott insulating behavior, and superconductivity. Among these, excitons—Coulomb-bound electron–hole pairs—represent the most fundamental quasiparticles in optically addressable semiconductor nanomaterials. These excitons exhibit diverse quantum characteristics shaped by charge, spin, valley, and layer degrees of freedom. At UC Riverside, my research is dedicated to unveiling the quantum nature of excitons within a rigorous symmetry framework. This includes studies on interlayer Rydberg excitons, interexcitonic hybridization, interlayer exciton-polarons, and layer-specific ferroelectricity. By engineering Stark-tunable coupling across atomic layers, this work advances both fundamental understanding of excitonic Coulomb correlations and practical pathways for developing layer-resolved integrated optoelectronic devices.
[S. Cha et al., submitted (2025)]
Lightwave-driven nonlinear physics
Lightwave-driven nonlinear physics
Light–matter interaction governs the coherent dynamics of photoexcited electrons. Leveraging the particle–wave duality of light, electrons perceive the optical field either as discrete quantized photons or as a continuous oscillating electromagnetic wave, depending on the excitation regime. Using high-harmonic generation (HHG) spectroscopy, we probe the nonlinear dynamics of massless Dirac fermions under varying charge densities, lightwave polarizations, and optical frequencies. This work systematically captures the crossover from the photon-dominated regime to the wave-driven regime, revealing the intricate evolution of electronic response under strong field.
[S. Cha et al., Nature Communications 13, 6630 (2022)]
Controllable electronic quantum degree-of-freedom
Controllable electronic quantum degree-of-freedom
Electronic quantum degrees of freedom—such as spin, valley pseudospin, and layer index—offer promising platforms for novel, controllable information units in next-generation semiconductor devices, potentially surpassing the fundamental limits of conventional device architectures. My research explores the electrostatic control of these quantum states at the device level, enabling systematic manipulation of quantum electronic properties in the coherent regime.
[S. Cha et al., Nature Nanotechnology 13, 910-914 (2018)]
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