Apr 9, 2025
4:30pm - 5:00pm
Summit, Level 4, Room 441
Michael Crommie1,2,Zhehao Ge1,2,Zehao He1,2,Qize Li1,2,Feng Wang1,2,Ziyu Xiang1,2,Jianghan Xiao1,2,Hongyuan Li3
University of California, Berkeley1,Lawrence Berkeley National Laboratory2,Cornell University3
Michael Crommie1,2,Zhehao Ge1,2,Zehao He1,2,Qize Li1,2,Feng Wang1,2,Ziyu Xiang1,2,Jianghan Xiao1,2,Hongyuan Li3
University of California, Berkeley1,Lawrence Berkeley National Laboratory2,Cornell University3
The behavior of electrons in materials depends strongly on the balance between electronic kinetic energy (KE) and Coulomb-driven electron-electron interactions (PE). When KE dominates then electrons become delocalized and behave like a liquid, whereas when PE dominates they can freeze into different crystal-like arrangements (“Wigner crystals”). Intermediate regimes where electrons transition between solid and liquid behavior are not well understood, especially in the presence of defects. I will discuss recent experimental advancements using scanning tunneling microscopy (STM) that enable this behavior to be visualized in 2D semiconducting systems involving transition metal dichalcogenide (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 landscapes. These include bare, unconstrained potentials, periodic moiré superlattices, domain wall boundaries, and artificial quantum dots. Electron density in these systems is controlled by incorporating TMD layers into field-effect transistor (FET) devices compatible with STM imaging at cryogenic temperatures. Electron crystallization and melting phenomena are observed to be strongly affected by charged defects and confinement potential dimensionality.