Non-Technical Abstract: Despite nearly two millennia of recorded study, magnetic materials continue to generate new fundamental discoveries and drive crucial progress in technologies such as sensing and information storage. Equally as intriguing is the recent emergence of a family of atomically-thin "two-dimensional" materials. It has grown rapidly to encompass materials with a broad range of technologically relevant properties, at the thickness of one thousandth of a human hair. However, a key component for the nano-nanotechnology tool box, an atomically thin magnet, is lacking. Our goal is to investigate a promising candidate, the magnetic semiconductor CrI3. Employing optical methods sensitive to magnetic properties, we will study its behavior as a function of thickness, from several tens of nanometers down to a single atomic layer. In addition, we will combine atomically-thin CrI3 with existing two-dimensional semiconductors to form atomically-thin heterostructures. This will enable us to explore emerging effects and functionalities occurring at the interface between the two materials. The proposed multidisciplinary research program provides an excellent platform for undergraduate and graduate students to explore new magnetic materials for potential impact in future computing platforms, data storage and consumer electronics.
The isolation of graphene has opened a new frontier in the physical sciences at the limit of a single atomic layer. Since this discovery, many 2D materials including semimetals, semiconductors and superconductors have been realized, but a 2D crystal displaying intrinsic ferromagetism has yet to be reported. Our goal is to investigate a promising candidate, the layered ferromagnetic semiconductor CrI3. Employing magneto-optical spectroscopy (photoluminescence, Raman, and optical Kerr rotation), we seek to understand its fundamental magnetic properties as a function of layer number, including Curie temperature, magnetic ground states, domain dynamics, and the possibility of electrically-tunable magnetism. Using this fundamental knowledge, we will engineer heterostructures formed by monolayer semiconductor WSe2 and ultra-thin CrI3. Spin sensitive optical techniques will enable us to investigate emerging spin/pseudospin phenomena in monolayer WSe2 caused by magnetic proximity effects, and develop new optically-driven spintronic devices such as spin-photovoltaics. In addition to breaking new ground in the experimental investigation of magnetism in the 2D limit, the proposed work may impact future computing platforms, data storage, and consumer electronics by enabling compact, energy efficient devices.