The main results are concluded following: we employed the quantum Liouville equation with phenomenological dissipation to investigate the transport properties of massless and massive Dirac fermion systems that mimics graphene and TIs, respectively. Graphene does not show an intrinsic Hall effect, but shows a Hall current under the presence of circularly-polarized laser fields as a nature of a optically-driven non-equilibrium state. Based on the microscopic analysis, we find that the light induced Hall effect mainly originates from the imbalance of photocarrier distribution in momentum space although the emergent Floquet–Berry curvature also has a non-zero contribution. In our last manuscript, we demonstrated that the magnetism in TI thin film could be dynamically manipulated via a Floquet engineering approach using circularly polarized light. Increasing the strength of the laser field, besides the expected topological phase transition, the magnetically doped TI thin film also undergoes a magnetic phase transition from ferromagnetism to paramagnetism, whose critical behavior strongly depends on the quantum quenching.
We systematically studied the electronic properties of Bi(111) thin films grown on a NbSe2 substrate. Combined with STM and the first-principles calculations, we found two types of non-magnetic edge structures coexist alternately at the boundaries of singe-bilayer islands, whose topological edge states exhibit remarkably different energy and spatial distributions. Prominent edge states are persistently visualized at the edges of both single and double bilayer Bi islands, regardless of the underlying thickness of Bi(111) thin films. Our work clarified the long-standing controversy regarding the topology of Bi(111) thin films and reveals the tunability of topological edge states via edge modifications. We also found that the dual-gate technology can well tune the electronic and topological properties of AFM even septuple-layer (SL) MnBi2Te4 thin films. Under an out-of-plane electric field, the Berry curvature of thin film could be engineered efficiently, resulting in a huge change of anomalous Hall signal. Beyond the critical electric field, the double-SL MnBi2Te4 thin film becomes a Chern insulator with a high Chern number of 3. These discoveries inspired the design of low-power memory prototypes for future AFM spintronic applications.
During the projects, we published four papers and one paper is under preparation. Our work was published in renowned Journals such like Physical Review Research, Physical Review B and New Journal of Physics
Furthermore the researcher participated in 7 dissemination activities i.e. conferences, seminars, invited talks and workshops in Germany, Spain, Belgium and USA (see list below) and also participated in the activities organized by the MPSD Theory Department for the DESY Open Day and Science Night, Hamburg, (2019 Nov.)
