† Department of Physics, Graduate School of Engineering, Yokohama National University, Yokohama 240-8501, Japan
‡ International Center for Materials Nanoarchitectonics,National Institute for Materials Science, Tsukuba 305-0044, Japan
§ CREST, Japan Science and Technology Agency, Kawaguchi 332-0012, Japan
∥ LxRay Co. Ltd., Nishinomiya 663-8172, Japan
⊥ Department of Applied Physics, National Defense Academy, Yokosuka 239-8686, Japan
Nano Lett., Article ASAP
DOI: 10.1021/nl503916t
Publication Date (Web): January 5, 2015
Copyright © 2015 American Chemical Society
*E-mail: (J.T.) jun@ynu.ac.jp., *E-mail: (Y.M.)minamiyasuo@ynu.ac.jp., *E-mail: (I.K.) katayama@ynu.ac.jp.
Improved control over the electromagnetic properties of metal nanostructures is indispensable for the development of next-generation integrated nanocircuits and plasmonic devices. The use of terahertz (THz)-field-induced nonlinearity is a promising approach to controlling local electromagnetic properties. Here, we demonstrate how intense THz electric fields can be used to modulate electron delocalization in percolated gold (Au) nanostructures on a picosecond time scale. We prepared both isolated and percolated Au nanostructures deposited on high resistivity Si(100) substrates. With increasing the applied THz electric fields, large opacity in the THz transmission spectra takes place in the percolated nanostructures; the maximum THz-field-induced transmittance difference, 50% more, is reached just above the percolation threshold thickness. Fitting the experimental data to a Drude-Smith model, we found furthermore that the localization parameter and the damping constant strongly depend on the applied THz-field strength. These results show that ultrafast nonlinear electron delocalization proceeds via strong electric field of THz pulses; the intense THz electric field modulates the backscattering rate of localized electrons and induces electron tunneling between Au nanostructures across the narrow insulating bridges without any material breakdown.
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