Topology and Impossible Electronic Devices - Andrea Young

Speaker: Andrea Young
Host: Dave Hsieh
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.
Date recorded: February 22, 2024
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