Research

Our group focuses on computational material science and theoretical condensed matter physics. We are interested in a broad range of novel quantum material physics and nanoscience. Our research activities are centered around developing new methodologies, conducting high-performance computations, and fostering experimental collaborations.

Below are some Highlights of our research areas.

Photoexcitation & Optoelectronics

Employing light to drive different phenomena or to induce and tune exotic phases of matter lies at the heart of modern condensed matter science and technologies such as optoelectronics. In emerging low-dimensional materials (like 2D atomically-thin layers and 1D nanotubes), due to enhanced Coulomb interactions from low-dimensional quantum confinement and reduced dielectric screening, photoexcited electron-hole pairs are strongly bonded to form excitons. Such strong exciton effects are crucially important in various photoexcitation phenomena and optoelectronics based on low-dimensional quantum materials and nanodevices, but are often overlooked in the non-interacting electron picture assumed in many theoretical approaches.

Our group is interested in investigating low-dimensional photoexcitation physics, particularly ultrafast and nonlinear optoelectronics, high-efficiency photovoltaics, excited-state dynamics, and nonequilibrium Floquet states, based on the ab initio many-body perturbation theory, including the time-dependent GW method (TD-GW) and GW plus Bethe-Salpeter equation (GW-BSE).

Relevant Publications

1D/2D Materials, Heterostructures

& Moiré Superlattices

By stacking different 2D material layers together — like playing with "atomic-layer LEGO toys" — a new material system known as van der Waals (vdW) heterostructures is created. These structures usually exhibit various emerging properties that are not present in individual layers. Pushing this innovation further, by stacking two layers with small lattice mismatches and/or different orientations, we can create another new playground — moiré superlattices — to explore novel physics like unconventional superconductors, topological phases, ferromagnetism, moiré electronics, and light-induced moiré excitons.

Our group is interested in a broad range of intriguing physical phenomena — electrical, topological, optical, electronic, magnetic, etc. — in low-dimensional quantum materials, particularly 2D atomically-thin layers, their heterostructures, and moiré superlattices. We explore these by developing and using multi-scale density functional theory (DFT) and beyond (such as GW), as well as effective models.

Relevant Publications

Topological Materials

Topological materials are a new class of quantum electronic matter with nontrivial topological states at their boundaries. Owing to topological protection, these novel states are robust to backscattering, making them ideal for low-dissipation electronic conducting channels — a key goal in high-performance circuit design.

We are interested in nontrivial topological materials and emerging topological phenomena from first-principles computations and effective models.

Relevant Publications

Nanoscale Quantum Transport

As the dimensions of electronic devices and circuits shrink to the nanoscale or even single-molecule levels, charge transport is dominated by quantum effects. This makes the standard circuit analysis inapplicable, thereby introducing a variety of novel quantum transport phenomena.

Our group is interested in novel nanoscale transport physics, both in fundamental science and practical device applications, based on ab initio quantum transport theory including nonequilibrium Green's functions method (NEGF). We focus on designing cutting-edge electronic devices with various transport functionalities, particularly single-molecule and spintronic devices, and collaborate closely with experimentalists.

Relevant Publications