This is very
interesting bit of work that is sure to lead to additional insight and testable
ideas. This is very much a test
platform. It is really nice.
Electrons have a
lot of internal structure and symmetries that would be nice to discern. This may
get us closer.
What is produced
is wave confined group of electron close to the offsetting holes that they were
freed from. It will be nice to throw
laser light at them to discover what is possible and much more.
Quantum
Dropleton: Weird New Particle Acts Like Liquid
By By Jesse Emspak,
Physicists can spend
years seeking new particles to illuminate aspects of nature's laws, but an
international team decided instead to make their own particles.
Called a dropleton or quantum droplet, the newly created
"particle" is actually a short-lived cluster of electrons and
positive charges called "holes." Like other so-called quasiparticles, dropletons act like single
particles.
At the Philipps-University of Marburg, Germany, and Joint
Institute for Lab Astrophysics at the University of Colorado, researchers made
an agglomeration of electrons and holes that was bigger than any created before
— 200 nanometers, or billionths of a meter, across. That is almost big enough
to see with a good microscope, about one-50th the
thickness of a cotton fiber. Before now, physicists had created two-pair groups
of electrons and holes, but never such an agglomeration that could form this
liquid-like quantum droplet or dropleton. [Wacky Physics: The Coolest Little Particles in Nature]
These dropletons behave according to the rules of quantum physics, and that means
scientists can use the particles to investigate how light interacts with matter
— a process also governed by quantum rules.
Because the dropletons are so large, in particle terms, they might
also help physicists locate the boundaries between the quantum world of the
very small and the classical world of the human scale, the physicists report in
the Feb. 27 issue of the journal Nature.
Making a dropleton
To make the dropleton, Mackillo Kira, a professor of physics at
Philipps University, and colleagues at the Joint Institute for Laboratory
Astrophysics in Colorado fired quick pulses of an extremely powerful laser at a
block of gallium arsenide, the same material used in red
light-emitting diodes (LEDs). Each pulse lasted less 100 femtoseconds, or
billionths of a billionth of a second. When the light hit the gallium arsenide,
the atoms released, or excited, electrons, which moved around in the gallium
arsenide like a gas or plasma. When the negatively charged electrons exited
their places around the atoms, they left behind regions of
positive charge called holes.
"In a sense, [dropletons] are particles whose properties are
largely determined by the environment, which makes them so exciting," Kira
told Live Science in an email. For instance, semiconductors work best, Kira
said, because the way their electrons are arranged makes it easier to excite
them.
Since the dropleton is an artificial particle, containing a number
of electrons, it acts something like a super-sized electron. That property
means physicists could essentially modify the size of an electron for
experiments. "This allows us to engineer … a man-made mass for an electron instead of the
universal constant measured in free space," Kira told Live Science in an
email.
Two-by-two
Of all the electron-hole particles that have been created, this is
the first to ever hold enough pairs to form a liquid-like droplet. [Liquid Sculptures: Dazzling Photographs of Falling
Droplets]
Electrons and holes, having opposite charges, tend to form pairs,
called excitons. These pairs are familiar to anyone who has used some types of
solar panels, which employ special materials to separate the electron-hole pairs,
freeing up electrons and generating current.
However, the excitons in this experiment were much
more energetic. They had so much energy that they would clump together in groups
as if they were water droplets clinging together. At that point, they were no
longer excitons bound in pairs — they were dropletons.
The electrons, unbound from single holes, formed a kind of
standing wave pattern around them. It's similar to the patterns that ordinary
molecules make in liquids (think of a stone thrown into the water and the
ripple pattern created), Kira said.
Dropletons don't last long, only 25 picoseconds, or trillionths of
a second. But that's actually a relatively long time in terms of
quantum-physical processes.
Kira added that the work suggests several interesting experiments.
For instance, the photons that excite the electrons to form dropletons become
entangled with the individual exciton pairs. That means it's possible to study
such interactions, an ongoing area of research.
In addition, because dropletons entangle with the photons used to
make the quasiparticles, physicists can use them to study storage of quantum
states — potentially useful in designing quantum-based communications devices
in which such states serve as the bits of information.
"The basic physical understanding obtained from these studies
can improve our ability to rationally design optoelectronic devices," such
as fiber-optic communications equipment, he said.
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