This illustration shows the arrangement of electrons and magnetic field lines that cause the particles to have fractional negative charge. Image: Science and T. S. Duff and T. Kovacs, AT&T Bell Laboratories |
While physicists at the Large Hadron
Collider smash together thousands of protons and other particles to see what
matter is made of, they’re never going to hurl electrons at each other.
No matter how high the energy, the little
negative particles won’t break apart. But that doesn’t mean they are
indestructible.
Using several massive supercomputers, a
team of physicists has split a simulated electron perfectly in half. The
results, which were published in Science,
are another example of how tabletop experiments on ultra-cold atoms and other
condensed-matter materials can provide clues about the behavior of fundamental
particles.
In the simulations, Duke
University physicist Matthew Hastings
and his colleagues, Sergei Isakov of the University
of Zurich and Roger Melko of the University of Waterloo
in Canada,
developed a virtual crystal. Under extremely low temperatures in the computer
model, the crystal turned into a quantum fluid, an exotic state of matter where
electrons begin to condense.
Many different types of materials, from
superconductors to superfluids, can form as electrons condense and are chilled
close to absolute zero, about -459 F. That’s approximately the temperature at
which particles simply stop moving. It’s also the temperature region where
individual particles, such as electrons, can overcome their repulsion for each
other and cooperate.
The cooperating particles’ behavior
eventually becomes indistinguishable from the actions of an individual. Hastings says the
phenomenon is a lot like what happens with sound. A sound is made of sound
waves. Each sound wave seems to be indivisible and to act a lot like a
fundamental particle. But a sound wave is actually the collective motion of
many atoms, he says.
Under ultra-cold conditions, electrons take
on the same type of appearance. Their collective motion is just like the
movement of an individual particle. But, unlike sound waves, cooperating
electrons and other particles, called collective excitations or quasiparticles,
can “do things that you wouldn’t think possible,” Hastings says.
The quasiparticles formed in this
simulation show what happens if a fundamental particle were busted up, so an
electron can’t be physically smashed into anything smaller, but it can be
broken up metaphorically, Hastings
says.
He and his colleagues divided one up by
placing a virtual particle with the fundamental charge of an electron into
their simulated quantum fluid. Under the conditions, the particle fractured
into two pieces, each of which took on one-half of the original’s negative
charge.
As the physicists continued to observe the
new subparticles and change the constraints of the simulated environment, they
were also able to measure several universal numbers that characterize the
motions of the electron fragments. The results provide scientists with
information to look for signatures of electron pieces in other simulations,
experiments, and theoretical studies.
Successfully simulating an electron split
also suggests that physicists don’t necessarily have to smash matter open to
see what’s inside; instead, there could be other ways to coax a particle to
reveal itself.
