Description
Electronic behavior depends on a balance between kinetic energy (KE) and electron-electron interactions (PE). When KE dominates, electrons become delocalized and behave like a liquid, whereas when PE dominates they freeze into different crystal-like arrangements (“Wigner crystals”). I will discuss recent experiments using STM that enable this behavior to be directly visualized in 2D semiconductors involving TMD materials. The ability to assemble individual TMD layers into van der Waals-bonded stacks allows the competition between solid and liquid electronic phases to be visualized for different 0D, 1D, and 2D energy landscapes. These include bare, unconstrained potentials, moiré superlattices, domain walls, and quantum dots. The electron density in these systems is controlled by incorporating TMD layers into field-effect transistor (FET) devices compatible with STM imaging. We observe that electron crystallization and melting phenomena are strongly affected by charged defects and the dimensionality of confinement potentials. Comparison of STM images to quantum Monte Carlo simulations helps to clarify the role of defects in electronic solid/liquid phase transitions.
