Physics Colloquium

Magnetism and superconductivity in rhombohedral trilayer graphene

Dr. Areg Ghazaryan
ISTplus Fellow, Institute of Science and Technology (IST) Austria

Abstract

Twisted bilayer graphene has emerged as an incredible system where energy bands can be made effectively flat by tuning the twist angle. This resulted in observation of interaction driven symmetry broken phases and superconductivity in twisted graphene systems. Unfortunately the band structure of those systems is quite cumbersome and hard to analyze theoretically for interaction effects. It turns out similar experimental signatures can be obtained even when the band is not completely flat, but the bandwidth is reduced considerably for a large range of momenta. This can be achieved by just stacking three layers of graphene in rhombohedral configuration. In this talk I will present the recent observation of magnetism and superconductivity in trilayer rhombohedral (ABC) graphene. I will show that a simple Stoner model is capable of capturing the main features of the interacting phase diagram. Finally, I will also discuss the possible origin of the superconductivity based on the Kohn-Luttinger mechanism, which only relies on electron-electron interaction and does not require the presence of phonons as mediators of the Cooper pairs.

Bio

I grew up in Yerevan, Armenia. I obtained my Bachelors, Masters and PhD degree from the Yerevan State University under the supervision of Prof. A. Kirakosyan and Prof. K. Moulopoulos (University of Cyprus) working mostly on electronic and optical properties of semiconductor nanostrucutres. After staying for two more years as a researcher at the same place, in 2013 I moved to University of Manitoba, Winnipeg, Canada for a postdoctoral position in the group of Prof. T. Chakraborty. There, I switched my research direction into numerical investigation of the fractional quantum Hall effect and other interacting topological phases. In 2016 I moved to the City College of New York, New York, US for my second postdoctoral position in the group of Prof. P. Ghaemi. There I got also involved in exciton-polaritons in novel 2D materials, defect states in iron based superconductors, while maintaining my fascination and interest with interacting topological phases of matter.

Since September 2018 I am an ISTplus fellow in the group of Prof. M. Lemeshko working on chiral induced spin selectivity, hybrid organic-inorganic perovskites, dipolar excitons and other related projects.