Physics Lecture Hall
Wednesday, November 19, 2014, 4:45 pm
Tea and cookies @ 4:30 pm
Custom low-dimensional material systems explored from atom to bulk
The ability to controllably layer atomically thin crystals into custom-made materials holds promise to realize physical systems with distinct properties that were previously inaccessible. The experiments described in this talk seek to uncover the unique nature of the charge carriers in such few-atoms-thick materials as well as effects that disorder and interlayer coupling have on their properties.
I will discuss scanning tunneling microscopy (STM) and spectroscopy (STS) experiments performed on graphene systems at low temperatures and in magnetic field. These techniques give access, down to atomic scales, to structural information as well as to the density of states. We find that twisting graphene layers away from the equilibrium Bernal stacking leads to the formation of Moire# patterns and results in a system with novel electronic properties tuned by the twist angle. Moreover, we study Landau quantization in graphene and its dependence on charge-carrier density. Performing spatially resolved STS/STM we demonstrate the true discrete quantum mechanical electronic spectrum within the Landau level band near an impurity in graphene in the quantum Hall regime.
Transition metal dichalcogenides also exhibit surprising behavior when their thickness approaches the atomic scale. I will discuss temperature-dependent Raman spectroscopy measurements that demonstrate how the number of layers in a crystal of 1T- TaS2 determines the different types of charge density order in this material, attesting to the important role of the inter-layer coupling.