[PAST EVENT] Physics Colloquium

November 2, 2012
Small Hall, Room 111
300 Ukrop Way
Williamsburg, VA 23185Map this location
Graphene is a two-dimensional honeycomb lattice of carbon atoms with remarkable electronic properties. While in many ways these make it an excellent candidate for microelectronic applications, the challenges of opening a gap in the electronic spectrum have limited its use in basic circuit elements such as transistors. In this talk I will review recent work in which an analog of such a gapped spectrum is induced by a time-dependent potential.

The resulting system turns out to have electronic structure with non-trivial topology, and is an example of a "Floquet Topological Insulator." It supports surprising fundamental behaviors -- including a quantized Hall effect with no magnetic field -- but there are fundamental challenges to predicting its electronic behavior in settings where it can be measured. I will present results of numerical calculations in which we meet some of these challenges, and show what should be found in the simplest possible measurement geometry, a two-terminal conductor. I will discuss the features of the results that demonstrate the unusual topology of the electronic structure, as well as surprising properties that are unique to the time-dependent nature of the system.