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Custom low-dimensional material systems explored from atom to bulk

Adina Luican-Mayer, Argonne National Laboratory
Monday, November 17, 2014 - 4:00pm to 5:00pm
PAA A-102

The ability to controllably layer atomically thin crystals into custom-made materials holds promise for realizing physical systems with distinct properties, previously inaccessible. The experimental results 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 interlayer coupling and disorder have on their properties. Firstly, 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 Moiré 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 STM/STS we demonstrate the true discrete quantum mechanical electronic spectrum within the Landau level band near an impurity in graphene in the quantum Hall regime. Secondly, 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.​

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