Colloquium: Dr. Trevor Arp | University of CA Santa Barbara

ABSTRACT: Optical excitons are metastable bound states formed from photoexcited electrons and holes. Excitons live short but rich lives in which they can interact with each other, with the host material, and with their surroundings. The rise of two dimensional (2D) materials has enhanced

our ability generate and study excitons due to the high engineerability of 2D heterostructures. The resulting increase in the strength and complexity of excitonic interactions opens many exciting doors for the physics of interacting many body phases and novel materials more broadly. The challenge is metrology; the short lifetimes of excitons combined with the limitations of far field optics holds back our ability to perform precision thermodynamic experiments on excitons. In this talk I will describe my journey through multiple experimental modalities to understand the physics that emerges from these interactions. First, I will discuss my work understanding the basic interactions of excitons in 2D transition metal dichalcogenides, both exciton-exciton interaction and interaction with the host material. Then I will discuss my work on the precision measurement of correlated electrons, combining nanoSQUID magnetometry with thermodynamic compressibility measurements to understand ferromagnetism, intervalley coherence, and spin-orbit coupling in rhombohedral graphene. Finally, borrowing the experimental concepts of correlated electrons, I will describe a path forward for exploring the novel physics of strongly interacting excitons.