Davisson-Germer Prize in Atomic or Surface Physics: Exploring the Atomic and Electronic Landscape of Low-Dimensional Materials

When materials are probed at the smallest length scales their quantum mechanical properties become highly apparent.  The scanning tunneling microscope (STM) provides an ideal tool for visualizing this behavior down to the atomic scale.  I will discuss how cryogenic scanning tunneling microscopy techniques can be used to both probe the local electronic properties of materials as well as to modify them via atomic manipulation.  This enables, for example, precise electron confinement structures (quantum corrals) to be constructed from individual atoms, thus providing a means to directly visualize the effects of electronic quantum interference at the nanoscale. Integration of these techniques with atomically-thin 2D materials such as graphene provides a completely new window into low-dimensional electronic behavior.  I will describe how characterization of graphene via cryogenic STM has enabled ultra-relativistic behavior such as atomic collapse and Dirac fermion quantum confinement to be directly imaged in gated graphene devices.  By reducing the dimensionality of graphene into 1D strips (i.e., graphene nanoribbons (GNRs)) it is possible to flexibly alter graphene’s electronic structure even further, ranging from tunable semiconducting behavior all the way to robust metallicity.  I will discuss how GNRs having different atomically-precise structures can be fabricated using “bottom-up” synthesis techniques involving molecular self-assembly and then interrogated via STM.  Such measurements have enabled the topological properties of GNRs to be directly visualized, thus providing a powerful new strategy for engineering the electronic properties of low-dimensional materials.