2D Device and Physics – Changjiang Yi
Two-dimensional (2D) materials devices and physics is currently one of the most compelling research areas in condensed matter physics. In the past few decades, numerous novel physical phenomena are discovered in 2D van der Waals (vdW) devices, including the unconventional superconductivity (SC), correlated electronic states, quantum spin Hall effect (QSHE), quantum anomalous Hall effect (QAHE), and fractional quantum anomalous Hall effect (FQAHE). 2D materials offer significant advantages for exploring and understanding new physics through tunability of symmetry and interaction of electrons, spins, and orbits.
Non-reciprocal transport in 2D materials
Abstract: Non-reciprocal transport indicates the directional flow of charge, spin, or orbital, which are intimately connected to the time reversal symmetry (T), inversion symmetry (P) and other crystalline symmetry (rotational axis, mirror, etc.). This phenomenon is typically the result of broken symmetries. The fabrication of 2D devices offers a promising avenue for the engineering of symmetries and intuitive tunability under electric and magnetic fields. The objective of this project is to explore the non-reciprocal transport properties, including the nonlinear Hall effect, the superconducting diode effect, and the magnetochiral effect, in 2D devices constructed using a variety of vdW materials that exhibit topological, superconducting, and magnetic properties.
Quantized transport of topological 2D materials
Abstract: Our research also focuses on investigating novel 2D materials that exhibit intriguing topological phenomena, including QHE, QSHE and QAHE. These phenomena have been the subject of extensive study in a number of systems, including the free electron gas, graphene, magnetic topological insulators and twisted TMD materials. In light of the preceding research, this project will concentrate on the exploration of new systems with narrow energy gaps and high charge mobilities for the fabrication of 2D devices and the measurement of transport properties with a view to observing quantized phenomena. Meanwhile, the project will also investigate the potential for observing quantum transport properties in 2D topological altermagnet through the manipulation of the symmetries.
2D device for topological and chiral nano-catalysis
Abstract: Another research interest is chiral catalysis based on 2D devices, which deeply connects chemistry and physics. The efficacy of chiral catalysis on single crystals is limited due to the challenge of the synthesis for homochiral single crystals. However, the fabrication of 2D materials allows for the straightforward construction of a chiral superstructure with opposite handedness, which is an intriguing approach for chirality-driven catalysis. In collaboration with the catalysis group at CPFS, we will employ the SECCM technique to conduct local detection on the artificial 2D chiral device. In light of this technique, we will also develop a setup for ion gating a 2d device with the objective of exploring novel physical properties.
In order to achieve the aforementioned proposals, we will focus on the fabrication of 2D devices based on vdW materials, including but not limited to topological materials, magnetic materials, superconductors, and ferroelectric materials. A variety of exfoliation techniques will be employed, including the use of standard scotch tape method, Al2O3-assisted method, ultra-thin metal-assisted method, and cold PDMS method. Subsequently, the 2D device will be constructed for the purpose of conducting charge transport measurements under tunable field and for the purpose of electrochemical catalysis.
This group has established close collaborative relationships with leading research groups at MPI-CPFS and other esteemed institutions, including Harvard University, Boston College, IFW, and SJTU-TDLT. These partnerships encompass a range of areas, including theoretical support, single crystal growth, characterization, and ARPES.