Refraction of Dirac Fermions across Molecular Graphene Junctions

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Graphene has been a subject of great interest in condensed matter physics due to its exotic topological properties. We have used an STM capable of individual atomic manipulation to engineer molecular graphene nanostructures which host relativistic massless Dirac fermions and constitute a fully-tunable electronic system. Motivated by this light-like behavior, our ultimate goal is to create a Veselago lens out of flakes of doped molecular graphene. This work explores the refraction of Dirac fermions across various types of molecular graphene junctions, including neutral-p, neutral-n, n-n, and neutral graphene - 2 dimensional electron system junctions. Principle to our analysis is a new technique combining the traditional quasi-particle interference method used in scanning tunneling microscopy with individual atomic manipulation, which allows us to investigate the scattering of electron wave functions in 2D systems with great precision. Finally, we also explore the possibility of ’tachyonic’ behavior of Dirac fermions as they refract across junctions from areas with higher to lower group velocities. We find significant evidence of refraction of Dirac fermions across various junctions, as well as propose a theoretical explanation for the angles of refraction based off of band structure. We also find evidence of ’tachyonic behavior’ in Dirac fermion refraction.


Type of resource text
Date created May 2021
Date modified April 7, 2023
Publication date May 18, 2021


Author Yankelevich, Beatriz
Degree granting institution Stanford University, Program in Engineering Physics
Thesis advisor Manoharan, Hari
Thesis advisor Dionne, Jennifer


Subject graphene
Subject molecular graphene
Subject condensed matter physics
Subject scanning tunneling microscopy
Subject individual atomic manipulation
Subject Veselago lens
Subject Dirac fermions
Subject refraction
Subject tachyonic behavior
Genre Text
Genre Thesis

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Yankelevich, Beatriz. (2021). Refraction of Dirac Fermions across Molecular Graphene Junctions. Stanford Digital Repository. Available at:


Undergraduate Theses, Program in Engineering Physics

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