Condensed Matter and AMO Seminar
October 17, 2019 - 3:00pm to 4:00pm
Howey Physics Building
Georgia State University
The reduced dimension in 2D materials results in large specific surface areas, making the surface/interfacial states play an essential role in determining their physical and chemical properties. Thus, the energy band model widely used for bulk materials may not provide a comprehensive description of 2D systems.
In this talk, Dr. Lei will introduce his efforts on studying the surface and interfacial states of 2D materials, especially their effects on the lateral and vertical transport in 2D system, which cannot be interpreted by the energy band model satisfyingly. Dr. Lei and his colleagues applied a lone-pair electron model to explain the evolution of energy levels in 2D materials, the formation of surface localized states, their activation and contribution to lateral transport. The similarity between the lone-pair electron model and the concept of Lewis base in coordinate chemistry further inspired an effective 2D materials surface functionalization method via the Lewis acid-base reaction.
This method opens new ways to tailor the intrinsic physical properties, and enable the fabrication of flexible organic-inorganic hybrid structure for sensing and energy harvesting. Besides the lateral transport, the unique vertical transport through the 2D layers also exhibits novel physical properties. Recently, a group of abnormal resonance tunneling peaks with an even energy distribution was observed on silicon-graphene tunneling junctions (micrometer scale). Lei’s team attributed the new observations to a quantum bound state originating from the abrupt dimensional changing between bulk semiconductor (silicon) and low dimensional system (graphene).
The team also raised the hypothesis of Fano-Feshbach resonance between the vertically distributed bound states and lateral scattering states (continuous band structure), which was supported by the experimental observation. This discovery will result in new electronic devices that can be applied in the further all-solid-state quantum logic or quantum sensor.
Dr. Lei received the Ph.D. of Applied Physics at Rice University in 2016, and then worked at the University of California, Los Angeles as postdoctoral researcher. In 2018, he joined the Department of Physics and Astronomy, Georgia State University as an assistant professor. His research focuses on low dimensional materials and quantum materials growth, surface quantum states controlling and transport property modification for new electronic/optoelectronic devices, advanced manufacturing of functional materials for sensing and energy applications, etc.