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Controlling avalanche criticality in 2D nano arrays

Yaalat-Chen Zohar (Hebrew University), Yossi Paltiel (HEBREW UNIVERSITY), Shira Yochelis (HEBREW UNIVERSITY), Grzegorz jung (Ben-Gurion University), Karin Dahmen (University of Illinois)

Slip Avalanches in Amorphous Metals

Mon 4:20 - 5:40

Barus-Holley 165

Many systems respond to slowly changing external force through avalanches spanning broad range of sizes. The same behavior of avalanches is found in various systems of different fields, ranging from macroscopic phenomena such as earthquakes, to microscopic interactions between magnetic domains. In our work we show that isomeric structural transitions in 2D nano array of organic self-assembled monolayer (SAM) exhibit critical dynamics with experimentally tunable criticality. The system consists of a sensitive field effect transistor (FET) coupled through SAM to illuminated semiconductor nanocrystals (NCs). Photoinduced Charges in the NCs are transferred through the SAM to the surface of the transistor and modulate its conductivity. Avalanches of isomeric structural transitions are revealed by measuring the current noise I(t) of the transistor. By the very nature of the structural transition avalanches, the avalanches statistics depends on the temperature of the molecules. More surprisingly, we found that criticality can be tuned during experiment at the same temperature. Accumulated surface traps charges reduce the dipole moment of the molecules, decrease their coupling, and thus decrease the critical disorder of the system. The rate of this process is determined by the illumination intensity affecting the charge flow towards the surface. Moreover, experiments show that the model of avalanche evolution depends on the length of the organic molecules, as a result of the different intermolecular coupling. In my talk I will present the new hybrid system in which avalanches occur. I will show that the investigated system provides a flexible and controllable tool box for experimental studies of critical dynamics in which the distance from the critical point can be in-situ changed during the experiments.