Niels Bohr Lecture by Andrea Young, University of California
Topology, correlations, and “impossible” electronic devices in graphene heterostructures
Abstract: 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 where a moire pattern generates an artificial superlattice. 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 direct current voltage step-up 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.
About the speaker
Andrea Young received his PhD from Columbia University in 2012. Following a Pappalardo Fellowship at MIT and stint as a visiting scientist at Weizmann Institute, he began his research group at UC Santa Barbara in 2015.
His research career has focused on the development of "van der Waals heterostructures" - interleaved sheets of two dimensional atomic layers - and using them as a platform to reveal the nature of collective states of electronic matter in two dimensions.
Besides nanofabrication and quantum transport techniques, his group has also specialized in ultra-sensitive magnetic scanned probes based on nanoscale superconducting quantum interference devices.
Coffee, tea and cake will be served outside Aud. 3 at 15:45
Niels Bohr Lectures er en engelsk-sproget foredragsrække på Niels Bohr Institutet med kendte forskere fra hele verden.
Foredragene holdes cirka 10 gange om året og er offentlige. De er for studerende og ansatte ved Niels Bohr Institutet samt andre med interesse for at høre om videnskabelig forskning i verdensklasse. Foredragene holdes på et ikke-teknisk niveau, hvor de kan forstås af alle med en baggrundsviden, der svarer til de første år på fysikstudiet.
Tidspunkt og sted: Hvis intet andet er anført, finder foredragene sted kl. 16.15 i Auditorium 3 på H.C. Ørsted Institutet, Universitetsparken 5, 2100 København Ø. Kaffe og kage serveres en halv time inden foredraget starter.
The lectures are public and held about 10 times a year. The lectures are for students and staff at the Niels Bohr Institute and others interested in worldwide scientific research. The lectures are held on a non-technical level where they can be understood by anyone with a background similar to the first year of physics study.
Time and place: Unless otherwise specified, the lectures take place at. 16.15 in Auditorium 3 at H.C. Ørsted Institute, Universitetsparken 5, 2100 Copenhagen Ø. Coffee and cake will be served half an hour before the lecture starts.