Controlling avalanche criticality in 2D nano arrays

Area of Science:

• Condensed Matter Physics
• Materials Science
• Surface Science

Background:

• Many physical systems exhibit avalanche dynamics in response to external forces or internal fluctuations.
• Disorder-induced critical phenomena are crucial for understanding complex system behavior, necessitating experimental probes with tuneable disorder.
• Previous studies have observed crackling noise in systems like neuronal activity and charge transfer in 2D molecular layers.

Purpose of the Study:

• To investigate critical dynamics in 2D organic self-assembled monolayers (SAMs) with experimentally tuneable disorder.
• To demonstrate that isomeric structural transitions in SAMs can exhibit avalanche behavior.
• To establish a model system for probing disorder-induced critical phenomena.

Main Methods:

• Fabrication of a field-effect transistor coupled to semiconducting nanocrystals (NCs) via a 2D organic SAM.
• Photoinduction of charges in NCs, followed by charge transfer through the SAM to the transistor surface.
• Measurement of transistor current noise I(t) to detect avalanches of isomeric structural transitions in the SAM.

Main Results:

• Isomeric structural transitions in the 2D organic SAM were observed to exhibit critical dynamics.
• Avalanche behavior, indicative of critical phenomena, was detected through transistor current noise measurements.
• Experimental tuning of disorder in the SAM was achieved by modulating accumulated surface charges, which alter molecular dipole moments and coupling.

Conclusions:

• 2D organic SAMs provide a tuneable platform for studying disorder-induced critical phenomena and avalanche dynamics.
• The observed critical dynamics are linked to isomeric structural transitions within the SAM.
• This work bridges theoretical models of critical phenomena with experimental investigations using tuneable disorder in molecular systems.