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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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