Modeling the electroluminescence of atomic wires from quantum dynamics simulations

Area of Science:

• Quantum mechanics
• Molecular physics
• Nanotechnology

Background:

• Existing quantum-mechanical methods simulate light emission from molecules but struggle with current-induced emission.
• Electromagnetic emission from input current has been a gap in molecular simulation capabilities.

Purpose of the Study:

• To develop and apply a novel simulation framework for calculating current-induced electromagnetic emission from nanostructures.
• To investigate the influence of electrical bias and molecular size on electroluminescence in metallic and semiconducting chains.

Main Methods:

• Utilized an equation of motion for the density matrix coupled to a photon bath (Redfield formulation).
• Employed the driven-Liouville von Neumann approach with open boundaries to simulate applied bias and current.
• Integrated the method with a self-consistent tight-binding Hamiltonian for nanoscale simulations.
• Calculated dissipated electromagnetic power from the time derivative of energy.

Main Results:

• Observed a complex interplay between bias and molecular length in semiconducting chains, with an optimal size for maximum emitted power at high voltages.
• Demonstrated that band bending in semiconducting chains, captured by the self-consistent method, explains this optimal behavior.
• Successfully computed electroluminescence in metallic and semiconducting chains, showing the effects of bias and size.

Conclusions:

• The developed methodology accurately quantifies current-induced electroluminescence in nanoscale systems.
• The findings provide insights into optimizing light emission from molecular electronic devices.
• The approach is extendable to more advanced quantum chemical Hamiltonians for broader applicability.