Terahertz-field-induced nonlinear electron delocalization in Au nanostructures

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Precise control over electromagnetic properties of metal nanostructures is crucial for developing advanced nanocircuits and plasmonic devices.
• Terahertz (THz) field-induced nonlinearity offers a promising avenue for dynamically controlling local electromagnetic properties at the nanoscale.

Purpose of the Study:

• To demonstrate the modulation of electron delocalization in percolated gold (Au) nanostructures using intense THz electric fields.
• To investigate the ultrafast nonlinear response of these nanostructures on a picosecond timescale.

Main Methods:

• Fabrication of isolated and percolated Au nanostructures on high-resistivity Si(100) substrates.
• Measurement of THz transmission spectra under varying intense THz electric field strengths.
• Analysis of experimental data using the Drude-Smith model to determine electron localization and damping parameters.

Main Results:

• Significant THz transmission opacity was observed in percolated Au nanostructures with increasing THz electric fields.
• A maximum THz-field-induced transmittance difference exceeding 50% was achieved near the percolation threshold.
• The Drude-Smith model analysis revealed strong dependencies of the localization parameter and damping constant on THz-field strength.

Conclusions:

• Ultrafast nonlinear electron delocalization is induced by strong THz electric fields, modulating electron backscattering rates.
• Intense THz fields facilitate electron tunneling between Au nanostructures across insulating bridges without causing material breakdown.
• This THz-field-induced control of electron delocalization in nanostructures is vital for future plasmonic and nanocircuit applications.