Laser spectroscopy and imaging of semiconductor and spintronic material

We use various types of laser spectroscopy and imaging techniques to study fundamental properties of materials, such as their electronic structures, optical transitions, and vibrational properties. To reveal such intricate hidden information of materials, we often cool them to cryogenic temperatures and apply magnetic/electric fields and microwave radiations.
Examples of materials we are currently interested in include two-dimensional semiconductors and magnets, one-dimensional semiconductor carbon nanotubes, and zero-dimensional quantum dots and molecules.

Related recent publications:

• Raman Shifts in Two-Dimensional van der Waals Magnets Reveal Magnetic Texture Evolution, Z. Huang et al. Nano Lett. 24, 1531 (2024)
• Lattice symmetry-guided charge transport in two-dimensional supramolecular polymers promotes triplet formation, R. Emmanuele et al. Adv. Sci. 11, 2402932 (2024)
• Encapsulating semiconductor quantum dots in supramolecular cages enables ultrafast guest–host electron and vibrational energy transfer, Lu et al. J. Am. Chem. Soc. 145, 5191 (2023)
• Observation of biexciton emission from single semiconductor nanoplatelets, L. Peng et al. Phys. Rev. Mater. 5, L051601 (2021)
• Bright and stable light emitting diodes made with perovskite nanocrystals stabilized in metal-organic frameworks, H. Tsai et al. Nat. Photon. 15, 843 (2021)

Near-field engineering for controlled light-matter interactions

When studying low-dimensional materials, it often becomes important to confine and localize light to length scales beyond the diffraction limit so as to strengthen light-matter interactions. We design and fabricate photonic resonators and cavities that are able to concentrate electromagnetic fields into subwavelength volumes for enhanced near field distributions.

Related recent publications:

• Polaritonic bright and dark states collectively affect the reactivity of a hydrolysis reaction, Y. Wang et al. ACS Photon. (2024)
• Amplified spontaneous emission from europium-based molecular complexes coupled to photonic crystal cavities, R. Emmanuele et al. Appl. Phys. Lett. 123, 061106 (2023)
• Room temperature lasing from semiconducting single-walled carbon nanotubes, J.-C. Chen et al. ACS Nano 16, 16776 (2022)
• Microcavity-modified emission from rare-earth ion-based molecular complexes, R. Emmanuele et al. ACS Photon. 9, 2315 (2022)
• Achieving extreme light confinement in low-index dielectric resonators through quasi-bound states in the continuum, W. Wang et al. Opt. Lett. 46, 6087 (2021)

Band structure engineering for emergent properties

Band structures of low-dimensional materials are susceptible to their surroundings. This provides unique opportunities for manipulating their properties to meet the requirements of specific applications. We apply a diverse range of methods to achieve control over band structures of materials, including using morphology, strain, chemical and defect engineering, with the goal of advancing these materials’ applications in quantum, electronic, and energy devices.

Related recent publications:

• Long-lived electronic spin qubits in single-walled carbon nanotubes, J.-S. Chen et al. Nat. Commun. 14, 848 (2023)
• Utilizing ultraviolet photons to generate single-photon emitters in semiconductor monolayers, W. Wang et al. ACS Nano 16, 21240 (2022)
• Trapping interlayer excitons in van der Waals heterostructures by potential arrays, D. J. Morrow et al. Phys. Rev. B 104, 195302 (2021)
• Creation of Single-Photon Emitters in WSe2 Monolayers Using Nanometer-Sized Gold Tips, L. Peng et al. Nano Lett. 8, 071115 (2020)

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