Physics Colloquium

Since the discovery of quantized Hall effects in the 1980s, topology has provided a useful new paradigm for understanding condensed matter systems, expanding our vocabulary for describing the distinctions between states of matter. 

I will focus on how topological properties can be harnessed to build otherwise impossible electronic devices--devices whose operation, in turn, provides precise tests of the topological description of matter.  In the first example, I will show how a quantized Hall effect can be realized at zero magnetic field from the spontaneous alignment of orbital magnetic moments in a graphene heterostructure. Remarkably, the large magnetic moments of the resulting chiral edge states can be used to realize a `magneto-electric' memory in which the magnetic moment can be controllably reversed through the application of an electrostatic potential. In the second example, I will show how the fractionalization of charge, characteristic of topologically ordered states, can be used to realize a dissipationless, purely DC (direct current) step-up voltage transformer. Along the way, I will introduce the physics of van der Waals heterostructures—layered stacks of atomically thin two-dimensional crystals—and show how the remarkable experimental control available in these systems has made them the leading platform for exploring the interplay of topology and many-body quantum physics. 

Join via Zoom:
https://caltech.zoom.us/j/81866929019
Meeting ID: 818 6692 9019

The colloquium is held in Feynman Lecture Hall, 201 E. Bridge.