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.