Theoretical seminar | 19 July 2023

Mr. Kirill Kapralov
Non-local dynamic conductivity of two-dimensional electronic systems and its manifestations in plasmonics

The dissertation work investigates the effect of non-local conductivity on plasma oscillations (mainly terahertz) in two-dimensional electronic systems.
- It is shown that the presence of transmission contacts in two-dimensional and one-dimensional electronic systems leads to an additional mechanism of plasmon damping associated with the leakage of electrons into the contacts. The damping rate of plasma oscillations associated with this mechanism in ballistic structures is of the order of the ratio of the Fermi velocity to the length of the structure.
- A theory of high-frequency two-dimensional electron transport in a magnetic field describing a ballistic-hydrodynamic transition is constructed, and an expression for the non-local high-frequency conductivity tensor is obtained.
- With the help of the constructed theory, the transformation of the magnetoplasmon dispersion during the transition from hydrodynamic to ballistic transport regime is described. The dispersion of two-dimensional magnetoplasmons with a decrease in e-e collisions  frequency splits at multiple cyclotron frequencies and in the ballistic limit takes the form of Bernstein modes.
- It is shown that the excitation of Bernstein modes in a two-dimensional electronic system can lead to asymmetric resonances in magnetoabsorption at multiple cyclotron frequencies. The possibility of excitation of these modes is due to the diffraction of incident radiation on metal contacts to a two-dimensional system.

1. Bandurin, D. A., Moench, E., Kapralov, K., Phinney, I. Y., Lindner, K., Liu, S., ... & Ganichev, S. D. (2022). Cyclotron resonance overtones and near-field magnetoabsorption via terahertz Bernstein modes in graphene. Nature Physics, 18(4), 462-467.
2. Kapralov, K., & Svintsov, D. (2022). Ballistic-to-hydrodynamic transition and collective modes for two-dimensional electron systems in magnetic field. Physical Review B, 106(11), 115415.
3. Kapralov, K., & Svintsov, D. (2020). Plasmon damping in electronically open systems. Physical Review Letters, 125(23), 236801.