The National Academy of Engineering recently recognized the top 20 achievements in the 20th century, which include electronics, computers, telephone, internet, imaging, laser, fiber optics, among others. Key to the development of these technologies are the advancement in solid-state devices over the last 50 years. These devices, such as transis- tors, amplifiers, light emitting diodes, magnetic tunnel junctions, lasers, and solar cells, have revolutionized the way information and energy are stored, processed, transmitted and utilized. Indeed, today’s society demand for innovations in solid-state technologies has never been greater. The isolation of atomically thin 2D graphene and discovery of new quantum and topological materials has opened the door to a wide range of new electrical and optical phenomena.

These new materials open opportunities to new devices and applications, and our research group is at the forefront of understanding their new device physics and designing of new electronics and nanophotonics. We are a theory and computational group interested in the understanding and design of nanomaterials and nanodevices. Towards this goal, we employed a range of multiphysics and multiscale tools both retrospectively (e.g. corroborating our results to experiments) and prospectively (e.g. predicting new phenomena and finding solutions to open problems). Our work in recent years is largely focused on the class of two-dimensional crystals and their heterostructures, topological and magnetic materials. We revealed their basic electronic and optical properties, and their opportunities for novel electronics, spintronics, optoelectronics, nanophotonics and plasmonics.

Postdoctoral and Visiting Scholar positions are available, please check with us by sending your resume to [email protected].

Highly motivated graduate and undergraduate students are welcome to participate in our research activities. Please refer to Publications and Google Scholar for more information about our research activities.


2D Materials Polaritons

In recent years, enhanced light-matter interactions through a plethora of dipole-type polaritonic excitations have been observed in two-dimensional layered materials. In graphene, electrically tunable and highly confined plasmon-polaritons were predicted and observed, opening opportunities for optoelectronics, bio-sensing and other mid-infrared applications. In hexagonal boron nitride, low-loss infrared-active phonon-polaritons exhibit hyperbolic behavior for some frequencies, allowing for ray-like propagation exhibiting high quality factors and hyperlensing effects. In transition metal dichalcogenides, reduced screening in the 2D limit leads to optically prominent excitons with large binding energy, with these polaritonic modes having been recently observed with scanning near field optical microscopy. Taken together, the emerging field of 2D material polaritonics and their hybrids provide enticing avenues for manipulating light-matter interactions across the visible, infrared to terahertz spectral ranges, with new optical control beyond what can be achieved using traditional bulk materials. We are leading a NSF-funded Engineering Frontier in Research and Innovation (EFRI) in search of new topological effects in 2D plasmons. This work is also supported by the NSF MRSEC at University of Minnesota.



Imagine a mirror where light reflected off its surface can be steered in any direction and its wavefront being manipulated at picosecond rate, as determined by the user through a set of electrical inputs to the mirror. Such “Snell’s law” defying optical phenomenon is made possible with artificial man-made surfaces, dubbed metasurfaces, where their materials optical properties can also be tuned by the application of electrical biases. If such a metasurface can be realized, this device could enable disruptive technologies such as optical routers and interconnects, where photons can be electrically routed at terahertz rates, hence making the current information transmission rate several orders of magnitude faster. Other applications include manipulation of far-field radiations for beam forming, scanners, multiplexers, and modulators. Together with experimentalists on campus and the Naval Research Labs, and with support from DARPA and NSF EPMD, we are designing various types of tunable metasurfaces using two-dimensional crystals and other metamaterials.


Electronics & Spintronics

Over the last fifty years, solid-state devices built using bulk three-dimensional materials, such as silicon, compound semiconductors, ferromagnets to organics, have played a pivotal role in the economic progress of our society. These devices, such as the transistors, light-emitting diodes, magnetic tunnel junctions, and lasers have revolutionized the way information are stored and processed. Indeed, the advent of information age has greatly capitalized on the miniaturization of the silicon transistor, allowing for faster and cheaper electronics. However, scaling down the transistor are becoming astronomically costly, information flow is burgeoning rapidly, and energy consumption increasing exponentially, today’s society demand for innovations in solid-state technologies has never been greater. With strong support from the CSPIN center, and a recent DARPA FRANC center, our goal here is to find a new type of switch, a different kind of switch, that would be extremely energy efficient and multifunctional, and probably work with a non-von Neumann computer architecture. Here, we begin our search from the bottom up, starting with novel materials such as topological insulator, semimetals, Heusler alloy, and 2D materials, to discover new device ideas exploiting the intrinsic material physics.  


2D Materials Heterostructures

The isolation of atomically thin 2D graphene ten years ago has opened door to an entire family of truly 2D layered crystals with a wide range of electrical and optical properties, with exciting possibilities for constructing new nanodevices and systems. Besides graphene, the family of 2D materials is rapidly expanding to include transition metal dichalcogenides, metallic oxides, metals, semimetals, semiconductors, and topological insulators; in total about several hundreds of them are known today. As Feynman eluded to, imagine the possibility of stacking these various layered materials in a controlled way to construct new composite system. Such a designers’ approach would allow one to envision materials systems with completely new electronic and optical properties on-demand, with potentially revolutionary impact on our ability to process light and electrons inside a tiny chip. Together with experimentalists on campus, we get support from the NSF supported Minnesota Nano center to explore hundreds of 2D materials heterostructures in search of novel material properties beyond what conventional bulk materials can offer.