Abstract
Abstract Thermally induced particle hopping in the nanoscale double-well potential is fundamental in material design and device operation. After the proposal of the basic hopping theory, several experimental studies, including some using the optical trapping method, have validated the theoretical approach over various friction ranges of the surrounding medium. However, only external parameters, such as viscosity, temperature, and pressures, have been varied in practical circumstances, and other tools capable of adjusting the potential profile itself to modulate the hopping rate are needed. By using metallic nanoantenna with various gap sizes and different optical pump power, we engineered a double-well potential landscape and directly observed the hopping of a single nanoparticle with a diameter of 4 nm. The distance between the two potential wells was 0.6–5 nm, and the maximum well depth and maximum height of the central potential barrier were approximately 69 and 4 k B T, respectively. The hopping rate was governed by the Arrhenius law and showed a vertex when the barrier height was approximately 2 k B T, which was in good agreement with the computational expectations.
Highlights
The thermally driven hopping of a particle between two stable states over a potential barrier is a fundamental process in various phenomena such as thermal diffusion in solids [1,2,3], electron transport in semiconductors [4,5,6], adatom diffusion at crystal surfaces [7, 8], chemical reactions [9, 10], and folding dynamics in biomolecules [11,12,13]
We investigated the hopping of a single quantum dot (QD) trapped in an optical double-well potential formed by a metal nanoantenna with a bowtie–shaped hole
The signal changes during the jumping were confirmed theoretically using finitedifference time-domain (FDTD) computations
Summary
The thermally driven hopping of a particle between two stable states over a potential barrier is a fundamental process in various phenomena such as thermal diffusion in solids [1,2,3], electron transport in semiconductors [4,5,6], adatom diffusion at crystal surfaces [7, 8], chemical reactions [9, 10], and folding dynamics in biomolecules [11,12,13]. The hopping behavior when modulating the potentials has not been sufficiently investigated because of the difficulty in manipulating the energy level of an optical potential [21]. Another challenge is that in conventional optical platforms adopting a dielectric focusing lens, the size of the optical trap cannot be reduced beyond the diffraction limit of light; this restricts the diameter of particles available in the experiment to greater than tens of nanometers. We investigated the hopping of a single quantum dot (QD) trapped in an optical double-well potential formed by a metal nanoantenna with a bowtie–shaped hole. The signal changes during the jumping were confirmed theoretically using finitedifference time-domain (FDTD) computations
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