Coupling Organic Molecules to Topological Insulators

By Andy S. Hewitt, PhD

Department of Physics, North Carolina State University

Abstract: 

The strong 3D topological insulators (TIs) are a class of bulk insulating materials with robust spin-textured surface states protected by time-reversal symmetry (TRS). Breaking TRS in these systems has been predicted to host exotic topological magnetoelectric effects and the quantum anomalous Hall effect. Typical approaches to breaking TRS have been to introduce magnetic dopants in the solid-solution synthesis. Another route is offered through magnetic molecules which have the advantage of, for example, tunable magnetic properties. It has been reported that a coupling may exist between the magnetic molecule manganese phthalocyanine (MnPc) and Bi₂Te₃. In this talk I will show evidence for a new hybrid-interface state existing at room temperature between MnPc and Bi₂Te₃ and show it to be localized at the molecular adsorption site. The interaction of the adsorbed molecules on the topological surface state will also be discussed. This interface system may have important implications for understanding the role of local TRS breaking in TIs and in controlling spin injection into these novel materials.

Bio:

Andy Hewitt received his Bachelors of Science in physics at North Carolina State University. During his undergraduate career his work on the growth and characterization of organic thin films earned 3 undergraduate research awards and 2 summer internships at the National Institute of Science and Technology in Gaithersburg, MD. He completed his Masters of Science in physics in 2014 at N.C. State University and started a multi-disciplinary collaboration to grow and characterize Topological Insulators. The main instruments he’s used to study these systems are photoelectron spectroscopy and scanning tunneling microscopy/spectroscopy. Andy will obtain his PhD this summer with a thesis entitled, “Coupling Organic Molecules to Topological Insulators”, under his advisor Prof. Dan Dougherty.