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Quantum Matter Seminar

Wednesday, January 25, 2023
4:00pm to 5:00pm
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East Bridge 114
Moiré Materials and their New Degrees of Freedom
Yuan Cao, Harvard,

Emergent phenomena often accompany the introduction of new degrees of freedom (DoFs) into a system. In condensed-matter physics, one manifestation of emergence is the complex phase diagrams in strongly-correlated electron systems. In recent years, the advent of low-dimensional materials enabled us to tailor the electrons in these systems via electrostatic gating. This capability is further boosted by the freedom of van der Waals stacking, allowing us to design and create arbitrary 2-dimensional material composites without constraints. These advances lead us to ask, are there more hidden DoFs in these already versatile material platforms?

In this seminar, I will talk about how we discovered that the moiré DoF in 2D materials, which originates from the twist angle in van der Waals stacks, can give rise to an arena of correlated electronic phases. Most intriguing is the observation of an unconventional superconducting state that arises when two sheets of graphene are twisted at a magic angle of 1.1 degrees. I will show that this is far from being a coincidence, but in fact the beginning of an entire family of moiré superconductors, all of which exhibit rich and unusual phenomenology. This research started a new field known as ‘twistronics', where we can now use moiré systems to study and create correlated quantum phenomena with unprecedented control. The physics of these moiré systems in turn will help us gain insight in understanding and creating other quantum materials.

For more information, please contact Tracy Mikuriya by email at [email protected].