With a
nano-ring-based toroidal trap, cold polar molecules near the gray shaded
surface
approaching the
central region may be trapped within a nanometer scale volume.
(September 17, 2015) Single
atoms or molecules imprisoned by laser light in a doughnut-shaped metal cage
could unlock the key to advanced storage devices, computers and high-resolution
instruments.
In a paper published in Physical Review A, a team composed
of Ali Passian of the Department of Energy’s Oak Ridge National Laboratory and
Marouane Salhi and George Siopsis of the University of Tennessee describes
conceptually how physicists may be able to exploit a molecule’s energy to
advance a number of fields.
“A single molecule has many degrees of freedom, or ways of
expressing its energy and dynamics, including vibrations, rotations and
translations,” Passian said. “For years, physicists have searched for ways to
take advantage of these molecular states, including how they could be used in
high-precision instruments or as an information storage device for applications
such as quantum computing.”
Catching a molecule with minimal disturbance is not an easy
task, considering its size – about a billionth of a meter – but this paper
proposes a method that may overcome that obstacle.
When interacting with laser light, the ring toroidal
nanostructure – sort of like a doughnut shrunk a million times – can trap the
slower molecules at its center. This happens as the nano-trap, which can be
made of gold using conventional nanofabrication techniques, creates a highly
localized force field surrounding the molecules. The team envisions using
scanning probe microscopy techniques to access individual nano-traps that would
be part of an array.
“The scanning probe microscope offers a great deal of
maneuverability at the nanoscale in terms of measuring extremely small forces,”
Passian said. “This is a capability that will undoubtedly be useful for future
trapping experiments.
“Once trapped, we can interrogate the molecules for their
spectroscopic and electromagnetic properties and study them in isolation
without disturbance from the neighboring molecules.”
While previous demonstrations of trapping molecules have
relied on large systems to confine charged particles such as single ions, this
new concept goes in the opposite direction, at the nanoscale. Next, Passian,
Siopsis and Salhi plan to build actual nanotraps and conduct experiments to
determine the feasibility of fabricating a large number of traps on a single
chip.