Measurement of Electronic Transport through 1G₀ Gold Contacts under Laser Irradiation

Abstract

Metal quantum point contacts (MQPCs) with dimensions comparable to the de Broglie wavelength of conducting electrons reveal ballistic transport of electrons and quantized conductance in units of G(0) = 2e(2)/h. We measure the transport properties of 1G(0) Au contacts under laser irradiation. The observed enhancement of conductance appears to be wavelength-dependent, while thermal effects on conductance are determined to be negligible. For wavelengths that are not absorbed by Au, the results are consistent with a photoassisted transport mechanism in which conductance depends both on the electronic structure of the leads and on the interaction of the transporting electrons with oscillating electric fields originating from excitation of local plasmons. For wavelengths absorbed by Au, photoinduced mechanism is suggested to be the dominant transport mechanism. The results demonstrate optical control of ballistic transport in MQPCs and are also important for future interpretation of light effects on the conductance of single-molecule junctions.

Quantum plasmonics: Symmetry-dependent plasmon-molecule coupling and quantized photoconductances

“…Similar prototype junctions have been realized experimentally by a scanning tunneling microscope or nanofabrication. [12][13][14][15][16][17][18] In accordance with experimental findings, all these junctions exhibit enhanced photocurrents at the plasmon resonances, whose intensities depend sensitively on the symmetry of molecular structures. For the chain connections, the coupling to longitudinal molecular excitations is dominant, leading to a nearly constant conductance.…”

Thermal conductance of metallic atomic-size contacts: Phonon transport and Wiedemann-Franz law

“…This paved the way for investigating a large variety of charge and energy transport properties in these atomic contacts such as electrical conductance [3,4], shot noise [5][6][7][8], photocurrent [9][10][11][12], thermopower [13][14][15][16], and Joule heating [17,18], just to mention a few. The mean free path for electrons and phonons is larger than the characteristic dimensions of atomic contacts [19], even at room temperature, and all the transport properties of these nanowires are therefore dominated by quantum mechanical effects.…”

Raman scattering from biased molecular conduction junctions: The electronic background and its temperature

“…Among these are observations of light emission from current carrying molecular junctions, 2,[19][20][21][23][24][25][26][27][28][29][30][31][32][33] affecting junction conduction properties and inducing DC currents by optical signals [34][35][36][37][38][39][40] and using optical pulses to cause conduction switching by affecting structural changes. [41][42][43][44][45][46][47][48][49][50][51] Relevant to our present discussion are recent demonstrations 12,13 that it can be used to determine the effective temperature in biased and current carrying junctions.…”