DRAFT

Materials Science Research Lecture

Wednesday, October 5, 2022
4:00pm to 5:00pm
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Noyes 147 (J. Holmes Sturdivant Lecture Hall)
Superconductivity, Strong Correlations, and Flat Electronic Bands in (un)-Twisted Graphene Multilayers
Stevan Nadj-Perge, Assistant Professor, Applied Physics and Materials Science, Caltech,

NOTE: Every student or postdoc (any option!) will receive a $5 SmartCash "coffee credit" for each Materials Research lecture attended. The credits will be tallied and issued after the last speaker of the term.

Abstract:

When two graphene sheets are rotationally misaligned (i.e., twisted) by approximately one degree and stacked together, the resulting bilayer exhibits various correlated, superconducting, and topological electronic phases. The origin of these distinctive phases, emerging at this particular twist angle, can be traced back to the weakly dispersive ('flat') electronic bands in which the kinetic energy of electrons is heavily suppressed, and interactions between electrons dominate.

In this talk, I will discuss several experiments providing insights into the electronic phases, band structure and symmetry breaking effects in twisted bilayer graphene obtained using scanning tunneling microscopy and cryogenic transport measurements. Then, I will give an overview of other graphene-based correlated and superconducting systems recently discovered in our lab, highlighting their striking similarities and differences. Besides twisted bilayers, we will discuss signatures of strong correlations and unconventional superconductivity in twisted tri-, quadri-, and penta-layers and compare these findings to the measurements of untwisted structures that can exhibit similar phenomenology in strong displacement fields. Finally, I will share thoughts on future opportunities in this research field and the potential of these materials for quantum science applications.

More about the Speaker:

Stevan Nadj-Perge joined Caltech in 2016 as an Assistant Professor of Applied Physics and Materials Science after obtaining his PhD at Delft University of Technology in the Netherlands and postdoctoral training at Princeton and Delft. His lab uses scanning tunneling microscopy and transport measurements to study novel electronic phases that emerge in carefully designed nanostructures due to the interplay of superconductivity, spin-orbit effects and strong electron-electron interactions.

Lately, his research has focused on two-dimensional materials and moiré systems. For his work, he received numerous awards, including the National Science Foundation Career Award, Alfred P. Sloan Fellowship, KNI-Wheatley Scholar, and Marko Jaric Award.

For more information, please contact Jennifer Blankenship by email at jennifer@caltech.edu.