Optical investigation of strong light-matter interactions in 2D materials
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371, Singapore
Abstract: Two-dimensional (2D) materials, such as graphene and monolayer transitional-metal-dichalcogenides (TMDs), have aroused great attention due to the underlying fundamental physics and the promising atomically-thin optoelectronic applications. Optical properties of these 2D materials are fundamentally interesting such as magneto-phonon resonance in graphene and strongexcitonic emission in monolayer WS2. Meanwhile, development of practical optoelectronics based on 2D materials is very promising, which opens many opportunities for the next-generation light-emitting applications such as valley light-emitting diodes and on-chip vertical-cavity surface-emitting lasers (VCSELs). Here, we report observations of magneto-phonon coupling effects in graphene layers, wealthy excitonic emission states of monolayer WS2,and 2D semiconductor lasing from monolayer WS2 embedded VCSELs. In particular, the triple G-mode splitting in graphene on graphite and the magnetic oscillations of the G-mode phonons in ABA- and ABC-stacked trilayer graphene samples have been probed by custom-designed micro-magneto Raman spectroscopy. By electrostatic and optical doping, tunable excitonic emission has been achieved due tointerplay of various excitonic states. Meanwhile, the doping dependences of excitons,trions, biexcitons and diverse bound excitons associated with impurities and structural defects have been discussed. Furthermore, we realize room-temperature low-threshold lasing from monolayer WS2 activated VCSELs under continuous-wave optical pumping, which are intrinsically compatible with the prevailingmonolithic integration technology.Overall, our studies provide many new understandings on fundamental light-matter interactions in atomically thin materials and paveways to developindustrially attractivelight-emitting applications based on 2D semiconductors.
Biography：Dr. Ting YU received his PhD from Department of Physics, National University of Singapore in 2003. Currently, he is a Professor in Division of Physics and Applied Physics, Nanyang Technological University, Singapore. Dr. YU has received many prestigious awards including Nanyang Excellence Award for Research and Innovation (2008), National Young Scientist Award, National Research Foundation Fellowship Award (2009), Outstanding Young Scientist for the 3rd Inter Academy Panel/World Economic Forum (Summer Davos Forum) ((IAP/WEF, Representative of Singapore, 2010) and Institute of Physics Singapore, Nanotechnology award (2011) et al. His research interests cover fabrication of low dimensional, especially 2D materials and investigation of their optical, optoelectrical and eletrochemical properties for developing novel electronics, optoelectronics and energy conversion/storage. Dr Yu has published more than 240 SCI papers (23 ESI highly cited) and received over 15,000 nonself-citations. His H-index is 68.