The unprecedented tunability of van der Waals materials enable charge density to be modulated over a large range. In the first half of the talk, I will focus on superconductivity in twisted bilayer graphene, in which the slow Fermi velocity and the small charge density appear to invalidate conventional BCS equations and present a paradox. The paradox is resolved by our experimental demonstration that the superfluid stiffness is dominated by the quantum geometric contribution. We also find that the band velocity in this Dirac superconductor constitutes a new limiting mechanism for the critical current, analogous to a relativistic superfluid.
In the second half of the talk, I will discuss transport in a 2D semiconductor in the regime of high large charge, revealing giant tunable intersubband transition and quantum Hall ferromagnetism.
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Meeting ID: 858 1199 4621
The colloquium is held in Feynman Lecture Hall, 201 E. Bridge.
In person is open to those with a valid Caltech ID.