Reviving Old Theories with 2D Materials. – (Ji Ung Lee/ Seminar / CEMES). – 10/09/2024, 11H

Séminaire invité FERMI

séminaire organisé par W Bacsa

Ji Ung Lee, College of Nanotechnology, Science, and Engineering, SUNY-Albany, Albany, NY.

Summary:
I will describe our efforts to revisit three theoretical concepts that are best demonstrated in 2D van der Waals (vdW) materials. Specifically, I will describe experimental realizations of, or our attempt to verify, these theories that were predicted decades ago using novel devices.

In the first part of my talk, I will describe the counterintuitive transmission of relativistic particles through a potential barrier, known as the Klein paradox. Here, the particles or quasiparticles are electrons that exhibit light‐like (photon‐like) characteristics in graphene. When these carriers impinge on a barrier, they transmit as if the barrier is not present. Nonrelativistic particles, such as electrons in a normal semiconductor, do not behave this way. Klein predicted these properties in the early days of quantum mechanics using the Dirac equation. The discovery of graphene has allowed us to demonstrate the Klein paradox in a condensed matter system.

In the second part of my talk, I will discuss Schottky barriers. A Schottky barrier forms at a metal‐semiconductor interface and is one of the fundamental devices in semiconductor technology. Ideally, the metal work function determines the barrier height, known as the Schottky‐Mott limit. This ideal description has been taught for decades, even though it had not been realized experimentally ‐ until recently. Typically, defect states form at the interface, which pin the metal Femi level. I will describe a Schottky junction formed at a vdW interface that obeys the Schottky‐Mott rule.

Finally, I will describe our efforts to find Majorana zero modes (Majorana fermions). A Majorana particle is its own antiparticle. I will discuss our use of EUV patterning techniques to accomplish this.