Berlin 2015 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 46: Transport: Nanomechanics (jointly with MM)

TT 46.7: Talk

Tuesday, March 17, 2015, 15:30–15:45, A 053

Nonlinear phononics using atomically thin membranes — Daniel Midtvedt and •Alexander Croy — Max-Planck-Institute for the Physics of Complex Systems, Dresden, Germany

In recent years, there has been considerable interest in tailoring material and wave-propagation properties using structured materials, prominent examples being phononic and photonic crystals. Here, we propose a design that allows for engineering flexural-phonon propagation by facilitating atomically thin membranes [1]. The strong geometric nonlinearity present in such systems leads to phonon-phonon interactions, which allow the study of many-body effects. Using a continuum mechanics description of a periodically pinned graphene membrane, we investigate the properties of the resulting phononic crystal and demonstrate that defects in the pinning lattice support localized modes. Two such modes in close proximity interact via the elastic energy, and constitute a simple model of a phononic dimer. We show that the defect Hamiltonian in the rotating-wave approximation is equivalent to a classical Bose-Hubbard model. By tuning the properties of the pinning lattice and the amplitudes of the flexural vibrations, we observe a bifurcation corresponding to the transition from “Rabi” to “Josephson” dynamics. Further, we demonstrate a wide tunability of the dimer frequencies by local back-gates, which allows for studies of the (non-linear) Landau-Zener transition.

[1] D. Midtvedt, A. Isacsson and A. Croy, Nat. Commun. 5, 4838 (2014).