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Nonconventional surface and edge effects in plasmonics

Date: 2017-12-07
Time: 10:30
Venue: 物理所M楼236
Speaker: Dr. Thomas Christensen

I will describe several, mainly theoretical, results in plasmonics which manifests aspects of either electronic or optical interface effects. Quantum corrections in nanoplasmonics exemplifies the former aspect; for structural feature-sizes or resonant wavelengths approaching the few-nanometer regime, the conventional, local description of electromagnetics breaks down due to its neglect of electronic spill-out, surface-enabled Landau damping, and nonlocality. In noble metals, a hydrodynamic model provides a decent effective remedy to the conventional approach, e.g. reproducing experimentally measured blueshifts [2] and regularizing several singular limits of the conventional approach [2]. Though popular and physically transparent, however, the hydrodynamic model is not a generic remedy due to its neglect of spill-out and surface-enabled Landau damping. I will discuss how a recently developed framework, based on the so-called Feibelman d-parameters, allows an analytical and straightforward account of all surface-related corrections with TDDFT-level accuracy [3]. In the realm of 2D plasmonics, I will discuss our prediction that finite graphene nanostructures may exhibit plasmonic quantum corrections distinct from those of their metallic counterparts, due to the existence of electronic edge states along zigzag terminations [4]. Finally, I will discuss our recent work on the prediction of high-frequency topological plasmonic edge modes in graphene under a magnetic bias [5] as well as the experimental measurement of low-frequency topological magnetoplasmonic edge modes in the 2D electron gas of a hetero-junction.

[1] S. Raza, S. Kadkhodazadeh, T. Christensen, M. Di Vece, M. Wubs, N.A. Mortensen, & N. Stenger, Multipole plasmons and their disappearance in few-nanometre silver nanoparticles, Nat. Commun. 6, 8778 (2015)
[2] T. Christensen, W. Yan, S. Raza, A.-P. Jauho, N.A. Mortensen, & M. Wubs, Nonlocal response of metallic nanospheres probed by light, electrons, and atoms, ACS Nano 8, 1745 (2014)
[3] T. Christensen, W. Yan, A.-P. Jauho, M. Soljačić, & N.A. Mortensen, Quantum corrections in nanoplasmonics: shape, scale, and material, Phys. Rev. Lett. 118, 157402 (2017)
[4] D. Jin*, T. Christensen*, M. Soljačić, N.X. Fang, L. Lu, & X. Zhang, Infrared topological plasmons in graphene, Phys. Rev. Lett. 118, 245301 (2017)
[5] T. Christensen, W. Wang, A.-P. Jauho, M. Wubs, & N.A. Mortensen, Classical and quantum plasmonics in graphene nanodisks: role of edge states, Phys. Rev. B 90, 241414(R) (2014)

Thomas is a graduate of the Physics and Nanotechnology program at Technical University of Denmark (DTU), BSc & MSc. Thomas completed his PhD under the supervision of Prof. N. Asger Mortensen in 2015, also at DTU, investigating classical and quantum corrections in metal and graphene plasmonics, for which he received DTU's Young Researcher Award and a Springer Thesis Award. Since 2016, Thomas has been a postdoc in the group of Prof. Marin Soljačić at Massachusetts Institute of Technology (MIT), studying plasmonics and topological photonics, funded by a Villum Foundation grant and a Sapere Aude grant from the Danish Research Council for Independent Research.

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