Dresden 2014 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 98: Transport: Nanomechanics

TT 98.9: Vortrag

Donnerstag, 3. April 2014, 17:30–17:45, BEY 81

Intrinsic mode-coupling and thermalization in nanomechanical graphene drums — •Daniel Midtvedt¹, Zenan Qi², Alexander Croy¹, Harold S. Park², and Andreas Isacsson¹ — ¹Chalmers University of Technology, Sweden — ²Boston University, Boston, MA, United States

Nanomechanical graphene resonators display strong nonlinear behavior, which leads to coupling between normal modes. This coupling allows for intermodal energy-transfer, which facilitates the redistribution of energy initially localized in a single mode. Further, the mode-coupling intrinsically limits the quality factor of the device. We study the mode-coupling in a circular graphene resonator using molecular dynamics and continuum mechanics. Mimicking a ring-down setup, the fundamental mode is excited with a given energy, and the time-evolution of this energy is computed. At T>0, we find a relaxation rate independent of system size and proportional to T^*/є_pre², where T^* is the effective temperature and є_pre is the pre-strain of the system [Midtvedt et al, arXiv:1309.1622]. At low temperatures, the system enters a metastable state where only very few low-frequency modes are excited, the life-time of which increases exponentially with decreasing excitation energy. This is similar to what is seen in the much studied Fermi-Pasta-Ulam (FPU) problem. We make a detailed comparison between the dynamics of a graphene drum and the FPU system, and propose to use graphene drums as test beds for FPU physics.