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Structurally Resolved 2D Materials: from Weakly Bound to Strongly Interacting

Adam Wei Tsen, Department of Physics, Columbia University
Monday, January 5, 2015 - 4:00pm to 5:00pm
PAA A-102

The electronic properties of materials are
intimately connected to their atomic structure. The formation of charge density
waves (CDWs) and spin density waves in various layered metallic chalcogenides,
for instance, directly coincides with a structural phase transition (such as a
periodic lattice distortion in the case of CDWs). In the past, studies on
monolayer graphene and various semiconducting dichalcogenides have shown that
taking layered materials to their physical 2D limit leads to fundamental
changes in band structure, allowing for an additional experimental knob to tune
for electronic functionality. However, the new structural phases of these
atomically thin materials have only been discovered more recently. In this
talk, I will focus on graphene and the layered CDW material 1T-TaS
2.
I will show via transmission electron microscopy how changes in their 2D
structure at different length scales (twin boundaries in bilayer graphene,
grain boundaries in polycrystalline graphene, and CDW domains in 1T-TaS
2)
further modify their electronic characteristics,
which we correlate using
transport measurements
. I will discuss the fundamental physics behind such
phenomena as well as demonstrate their use in developing novel electronic
devices.

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