Acoustic plasmons at the crossover between the collisionless and hydrodynamic regimes in two-dimensional electron liquids

Tuesday, June 4, 2019 - 2:00pm - 3:00pm
Lind 409
Marco Polini (Istituto Italiano di Tecnologia)
Hydrodynamic viscous flow in two-dimensional electron systems has so far been probed only by dc transport [1-4] and scanning gate microscopy [5] measurements. In this talk I will discuss theoretically signatures of the hydrodynamic regime in a near-field optical microscopy setup [6]. I will describe a theory of the dispersion relation of acoustic plasmon modes in two-dimensional electron liquids, which is based on a non-local conductivity that takes into account the effects of (momentum-conserving) electron-electron collisions, (momentum-relaxing) electron-phonon and electron-impurity collisions, and many-body effects beyond the celebrated Random Phase Approximation. I will illustrate our main results for the dispersion and, most importantly, the damping of acoustic plasmon modes and their coupling to a near-field probe, identifying key experimental signatures of the crossover between collisionless and hydrodynamic regimes.

Work supported by the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 785219 “Graphene Core2”

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[2] R. Krishna Kumar, D.A. Bandurin, F.M.D. Pellegrino, Y. Cao, A. Principi, H. Guo, G.H. Auton, M. Ben Shalom, L.A. Ponomarenko, G. Falkovich, K. Watanabe, T. Taniguchi, I.V. Grigorieva, L.S Levitov, M. Polini, and A.K. Geim, Nature Phys. 13, 1182 (2017).
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[5] B.A. Braem, F.M.D. Pellegrino, A. Principi, M. Röösli, S. Hennel, J.V. Koski, M. Berl, W. Dietsche, W. Wegscheider, M. Polini, T. Ihn, and K. Ensslin, Phys. Rev. B 98, 241304(R) (2018).
[6] I. Torre, L. Vieira de Castro, B. Van Duppen, D. Barcons Ruiz, F.M. Peeters, F.H.L. Koppens, and M. Polini, Phys. Rev. B 99, 144307 (2019).