IQIM Postdoctoral and Graduate Student Seminar

Abstract: While graphene has been dubbed as a ‘wonder material' because of amazing characteristics such as the ability to conduct electricity better than copper and being two hundred times stronger than steel, until recently, the key quantum phenomenon of superconductivity was missing from the list of properties exhibited by graphene. In 2018, an astonishing discovery showed that by placing two sheets of graphene on top of each other which are rotationally misaligned by a small angle - in a structure known as Twisted Bilayer Graphene (TBG), it is possible to realize superconductivity when the rotation angle is close to the ‘Magic Angle' value of 1.1 degrees[1]. More surprisingly, superconductivity in the initial reports was observed in close proximity to insulating states - resembling the phase diagram of High Tc superconductors. This sparked a fierce debate about its origin and its possible relation to High Tc superconductors. In this talk, I will show that by carefully engineering the dielectric environment of TBG, it is possible to stabilize superconductivity in non-magic angle TBG devices without the presence of any insulating states[2]. This discovery imposes severe constraints on the origin of superconductivity in TBG. I will also discuss measurements providing direct evidence of spin-orbit coupling induced in TBG for the first time. I will conclude by talking about possible experiments that will shed more light on the nature of superconductivity in TBG.

[1] Cao et al. "Unconventional superconductivity in magic-angle graphene superlattices." Nature 556, 43–50 (2018).

[2] Arora et al. "Superconductivity in metallic twisted bilayer graphene stabilized by WSe2" Nature (2020) In press. Preprint available at https://arxiv.org/abs/2002.03003

Attend the talk at: https://caltech.zoom.us/j/97280252054

This week's talk will be presented live only, it will not be recorded.