Quantum mechanics, developed in the 1920s, has had an
enormous impact in explaining how matter works. The elementary particles that
make up different forms of matter—such as electrons, protons, neutrons, and
photons—are well understood within the model quantum physics provides. Even
now, some 90 years later, new scientific principles in quantum physics are
being described. The most recent gives the world a glimpse into the seemingly
impossible.
Prof. Eran Rabani of Tel Aviv Univ.’s School
of Chemistry and his colleagues at Columbia Univ. have discovered a new quantum
mechanical effect with glass-forming liquids. They’ve determined that it’s
possible to melt glass—not by heating it, but by cooling it to a temperature
near absolute zero.
This new basic science research, to be published in Nature
Physics, has limited practical application so far, says Prof. Rabani. But
knowing why materials behave as they do paves the way for breakthroughs of the future.
“The interesting story here,” says Prof. Rabani, “is that by
quantum effect, we can melt glass by cooling it. Normally, we melt glasses with
heat.”
Turning the thermometer upside-down
Classical physics allowed researchers to be certain about the qualities of
physical objects. But at the atomic/molecular level, as a result of the duality
principle which describes small objects as waves, it’s impossible to determine
exact molecular position and speed at any given moment—a fact known as the
“Heisenberg Principle.” Based on this principle, Prof. Rabani and his
colleagues were able to demonstrate their surprising natural phenomenon with
glass.
Many different materials on earth, like the silica used in
windows, can become a glass—at least in theory—if they are cooled fast enough.
But the new research by Prof. Rabani and his colleagues demonstrates that under
very special conditions, a few degrees above Absolute Zero (?459.67°
Fahrenheit), a glass might melt.
It all has to do with how molecules in materials are
ordered, Prof. Rabani explains. At some point in the cooling phase, a material
can become glass and then liquid if the right conditions exist.
“We hope that future laboratory experiments will
prove our predictions,” he says, looking forward to this new basic science
paving the way for continued research.
Classical glass
The research was inspired by Nobel Prize winner Philip W. Anderson, who wrote
that the understanding of classical glasses was one of the biggest unsolved
problems in condensed matter physics. After the challenge was presented,
research teams around the world rose to it.
Until now, structural quantum glasses had never been
explored—that is, what happens when you mix the unique properties in glass and
add quantum effects. Prof. Rabani was challenged to ask: if we looked at the
quantum level, would we still see the hallmarks of a classical glass?
What the researchers unearthed is a new and unique
hallmark, showing that quantum glasses have a unique signature. Many materials
he says can form a glass if they’re cooled fast enough. Even though their
theory is not practical for daily use: few individuals own freezers that dip
down nearly 500 degrees below zero.
Prof. Rabani is currently on sabbatical at the Univ. of California,
Berkeley, as a
Miller Visiting Professor.
