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Physicists love particles,\hand with good reason – almost everything in the universe
is made up of particles, so the physicist’s approach to understanding the universe is
to understand the particles that make it up. If you want to discover and catalogue new
particles (which physicists do), here are three approaches you can take.
First, you can take old particles we already know stuff about and just stick them together
to build new *composite* particles. That’s what chemists and molecular biologists spend
a lot of their time doing, and it’s kind of like figuring out what you can build with
legos.
Second, you can smash old particles together with ever increasing violence, either hoping
to break an old particle apart into previously unknown constituents or to excite a new particle
into existence from the quantum fields that underly all reality. Sometimes this works
and the smashing reveals an entirely new *fundamental* building block of the universe like quarks
or the Higgs boson. But most of the time it just makes a big mess, an explosion of old
particles we already know about.
Third, you can put old particles in new environments so that they behave differently, or put old
particles together in new ways so that new particle-like behaviors emerge through their
*collective* quantum interactions.
For example, in certain crystals, the particles that move around are not electrons themselves
but in fact holes or gaps in a densely packed sea of electrons.
Or, when you make certain materials really really cold, free electrons in them stop acting
like electrons and team up in pairs to act like weird electron-only atoms that move around
with essentially no resistance.
Or when you make certain metals really cold, electrons in them start acting as if they
were 1000 times *heavier* than normal.
Or if you make a super thin essentially 2-dimensional sheet of gallium arsenide with a perpendicular
magnetic field and parallel electric field and make it really cold, electrons start behaving
as if they had an electric charge that’s a fraction of what they normally do.
Or if you force electrons into a special 1-dimensional line, the particles that move back and forth
along that line *look* like electrons, except separated so that some of them have the charge
of an electron but no spin, while others have the spin but no charge.
Or if you cool helium down super super cold, you’ll find emergent particles that behave
like higgs bosons! These emergent higgs bosons were first discovered in 1973, 40 years before
the higgs boson fundamental particle was discovered at the Large Hadron Collider by violently
smashing together protons.
Of course, the particles that emerge when you put collections of electrons together
in materials aren’t fundamental constituents of the universe, but they’re far more diverse
and bizarre and weird and cool. And unlike searching for fundamental particles where
you just have to wait and see what nature has in store, we can actively find and curate
new emergent particles simply by making different weird materials that allow their emergent
properties to come to life. Plus, materials with emergent particles have real and far-reaching
practical technological use: in electronics, computer chips, levitating high speed trains,
and even the magnets and detectors used to discover the higgs boson at the Large Hadron
Collider.
This video was supported in part by the Gordon and Betty Moore Foundation’s Emergent Phenomena
in Quantum Systems Initiative. EPiQS supports discovery-driven research on novel electronic
materials and aims to stimulate breakthroughs to fundamentally change our understanding
of the organizing principles of complex matter. To learn more, visit Moore.org or follow the
Moore foundation on twitter.