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Topology and “impossible” electronic devices

Andrea Young, UC Santa Barbara
Monday, December 4, 2023 - 4:00pm
PAA A-102

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 an electrically actuated magnetic memory, where the macroscopic magnetic moment can be controllably reversed through the application of a 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 purely DC (direct current) and nearly dissipationless 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. 

Video Link (requires UW NetID)

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