Physics Program Presents
Novel Electronic Transport in Topological Insulators and 2D Semimetals
Friday, May 13, 2016
Hegeman 107
12:00 pm EDT/GMT-4
12:00 pm EDT/GMT-4
Valla Fatemi, Massachusetts Institute of Technology
The notion of symmetry-protected topological order in electronic systems has transformed our understanding of condensed matter systems. This notion led to the prediction and discovery of quantum spin Hall systems, 3D topological insulators, topological semimetals, and more. However, electronic transport measurements of such systems have been notoriously challenging due to the difficulty of synthesizing high purity crystals and fabricating devices without causing degradation. To surmount these challenges, we have developed techniques for fabrication of van der Waals heterostructure devices in a controlled environment. In our electronic transport measurements, conducted at cryogenic temperatures, we utilize electrostatic gates and large magnetic fields as powerful experimental knobs. First, I will present our work on the realization of independently accessible surface states on the 3D topological insulator Bi1.5Sb0.5Te1.7Se1.3. Second, I will discuss our more recent experiments on WTe2, which is expected to be a quantum spin Hall system in the monolayer and has a large, non-saturating magnetoresistance in its 3D form. By thinning the crystal to a few atomic layers, the magnetoresistance can be turned on and off by changing the carrier density, which can be modeled as a transition from a semimetal to a simple metal. This is a promising step toward the realization of 2D van der Waals topological systems.For more information, call 845-752-7302, or e-mail [email protected].
Time: 12:00 pm EDT/GMT-4
Location: Hegeman 107