Abstract: One of the landmarks of quantum mechanics was the classification of metals, insulators and semiconductors according to their band structures. Such understanding laid the foundation of modern technologies: We realize electronic, optoelectronic and photonic devices by leveraging materials with distinct band structures. With the ever-growing quest for more advanced devices, there is an increasing need for new device principles. Such a need strongly resonates with the recent discoveries of novel quantum physics in new quantum materials. The discoveries of topology and Berry phase physics have opened up new dimensions for device design and engineering. Advances in 2D van der Waals materials have provided unprecedented tunability over material and device properties.
In this talk, I will show how modern quantum condensed matter physics and novel quantum materials can lead to new, robust electronic and optoelectronic devices, with potential applications in sensing, communication, computation, etc. First, I will show our observation of intrinsic photocurrent generation in charge neutral graphene devices and topological materials (TaAs and monolayer WTe2) devices. In terms of fundamental physics, these novel photocurrents uncover new Berry phase and nonequilibrium electron-electron interaction effects. In terms of potential applications, these intrinsic photocurrents provide a new scheme for efficient, fast photodetection in the infrared and terahertz regimes in a homogeneous quantum material without any p-n junctions. Second, I will describe our observation of the nonlinear Hall effect in the 2D quantum ferroelectric semimetal, bilayer WTe2. This is a new type of electrical Hall effect realized in a nonmagnetic material and without external magnetic field. This effect provides a new mechanism for rectification and micro-scale energy harvesting based on the intrinsic quantum Berry phase effect. Looking forward, I will discuss broadly how the emerging quantum properties in novel quantum materials can be harnessed to realize a wide range of new quantum technologies.
Bio: Dr. Qiong Ma got her Bachelor’s degree from the University of Science and Technology of China (USTC). She then moved to MIT where she got her Ph.D. in physics under the supervision of Prof. Pablo Jarillo-Herrero. She is now continuing as a postdoc in the Jarillo-Herrero’s group and in close collaboration with Prof. Nuh Gedik. Dr. Ma’s research focuses on discovering and understanding fundamentally new optical, electronic and optoelectronic phenomena in novel quantum materials. She is especially interested in novel quantum properties that lead to large device responsivities, potentially providing new pathways for the development of quantum technologies. Dr. Ma was selected for the 2018 Rising Star in Physics workshop at MIT.
Host: Tayo Akinwande