Condensed Matter Seminars

If one can control the atomic symmetries of a material at will, the intrinsic properties of the material will be significantly modified. However, the atomic structures of conventional materials are often constrained by the equilibrium phase of matter. Here, we overcome this fundamental limitation using recent advances in twistronics, enabling precise control over all the individual point group symmetry elements – inversion, mirror, and rotational symmetries – in twisted van der Waals (vdW) material in a new 3D configuration [1]. The resulting 3D twisted materials exhibit emerging optical responses that are fundamentally different from those of natural vdW materials. This novel approach to control symmetries can enable nearly infinite vdW quasicrystalline phases, promising a practical platform to study less-explored structure-property relationships of quasicrystals. In addition, we will discuss an ultraclean vdW crystal synthesis method [2]. A self-flux synthesis method we developed has yielded vdW materials with ~ 2 orders of magnitude lower point defect density compared to commercial vdW materials grown by a chemical vapor transport method. These ultraclean vdW materials reveal intrinsic excitonic properties that were previously obscured by low-quality materials. The combination of these ultraclean materials with the symmetry design approach holds great promise for the development of high-performance artificial material systems for next-generation technologies.

References:

1. Bumho Kim, Jicheng Jin, Zhi Wang, Li He, Thomas Christensen, Eugene J. Mele, and Bo Zhen, Nature Photonics 18, 91-98 (2024).
2. Bumho Kim, Yue Luo, Daniel Rhodes, Yusong Bai, Jue Wang, Song Liu, Abraham Jordan, Baili Huang, Zhaochen Li, Takashi Taniguchi, Kenji Watanabe, Jonathan Owen, Stefan Strauf, Katayun Barmak, Xiaoyang Zhu, and James Hone, ACS Nano 16, 140-147 (2022).