Photonics in Materials

Photonics in Materials

Keywords: Raman spectra, Photovoltaics, Photocatalysis, Second harmonic generation, Excitons effect

Linear and nonlinear optical response of 2D materials

Two-dimensional (2D) materials are widely applied across many research areas, including photovoltaics, nanoelectronics, and thermoelectricity. Recent advances in top-down and bottom-up synthetic approaches enable the production of 2D crystals with precise and unique optical, mechanical, and electronic properties. In these applications, optical properties play an essential role. In this topic, we study the relevant fields of photonics of the 2D materials and heterostructures by the first-principles calculations, including the linear response, nonlinear response, excitons effect, nonlinear second harmonic generation (SHG), etc, for the applications on photovoltaics, water splitting, laser technology.

Resonance Raman spectroscopy

Resonance Raman spectroscopy is a powerful tool for characterizing 2D materials, providing insights into their electronic and vibrational properties, especially when the incident laser energy matches the material’s electronic transitions, revealing features like double resonance Raman processes and allowing for the study of electron-photon, electron-defect, and electron-phonon interactions. For example, the resonance Raman spectroscopy can reveal information about the G and 2D bands in graphene, which are related to the vibrational modes of the material. However, Raman calculations at the first-principles level are challenging due to the complexity of the interactions. We are pioneering in this field. We are pioneering in this area. We have developed two first-principle resonant Raman computational codes, QERaman and QR2-code to calculate the single- and double-resonance Raman spectra, respectively. In this topic, our goal is to search for new physics behind Raman spectra.

Selected Publications

  1. D. P. Gulo, N. T. Hung, R. Sankar, R. Saito and H. L. Liu, Exploring optical properties of 2H- and 1T’-MoTe2 single crystals by spectroscopic ellipsometry, Phys. Rev. Mater. 7, 044001-1-13 (2023).
  2. V. V. Thanh, D. V. Truong and N. T. Hung, Janus γ-Ge2SSe monolayer as a high-performance material for photocatalysis and thermoelectricity, ACS Appl. Energy Mater. 6, 910-919 (2023).
  3. S. Han, Y. Zhao, N. T. Hung, B. Xu, R. Saito, J. Zhang and L. Tong, Complex Raman tensor in helicity‑changing Raman spectra of black phosphorus by circularly polarized light, J. Phys. Chem. Lett. 13, 1241–1248 (2022).
  4. V. V. Thanh, N. D. Van, D. V. Truong, R. Saito and N. T. Hung, First-principles study of mechanical, electronic and optical properties of Janus monolayer of transition metal dichalcogenides, Appl. Surf. Sci. 526, 146730-1-8 (2020).