EMERGE · Tuning Emergent Phases in 2D Materials

Tuning Emergent Phases in 2D Materials

The primary aim of this project was to study the electronic phases which emerge when layered materials are thinned to the two-dimensional limit and interfaced with other crystalline surfaces. For the past 15 years, researchers have had the experimental ability to isolate monolayers of crystalline solids on surfaces; this initial surge of research has revealed that the environment surrounding such two-dimensional crystals can play a large role in the observed properties of the materials’ themselves. In certain contexts, it is even possible for interfacial effects to produce entirely new or emergent properties, which are not present in the isolated two-dimensional material. The range of possible emergent properties in two-dimensional materials is extremely broad, which means these properties can be used in applications from computation to optoelectronics to energy transmission and importantly, help society deal with large scale problems related to the energy used in computation and data storage, the efficient transmission of energy over large distances, and the efficient conversion of light to electricity. As all emergent properties of two-dimensional materials is a global scale research effort, this project has chosen to focus on the specific properties of a unique class of two-dimensional materials – three atom thick metallic sheets. The objectives were to study how these sheets behave and are modified by their interaction with the surfaces which support them. To achieve this primary goal, we developed a new procedure to synthesize these new two-dimensional materials (in this case vanadium sulfide) under extremely clean conditions on atomically pristine single crystal metal substrates (gold). Using ultra-low temperature atomic scale microscopy to study the resulting 2D material, we were able to successfully characterize the emergent electronic phase in the vanadium sulfide. We were able to show that a geometric effect (termed Moire effect), which is observed between two periodic surfaces, drove an electronic phase transition to a charge density wave ground state. We could prove that these Moire effects were actually the cause of this electronic phase transition by observed the way these electronic changes behaved when the Moire structure was modified (for instance by changing the angle of the vanadium sulfide monolayer). This direct observation of correlated electronic ordering and surface geometric effects shows that not only do electronic phases emerge in this particular 2D material, but implies that we can also control them via their interfaces with other materials. Ultimately, dynamic control of this electrical state could be used to store information in next-generation memory devices.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз