In the last three decades, condensed matter physicists have discovered a wonderland of exotic new phases of matter: emergent, collective states of interacting particles that are nothing like the solids, liquids and gases of common experience.
The phases, some realized in the lab and others identified as theoretical possibilities, arise when matter is chilled almost to absolute-zero temperature, hundreds of degrees below the point at which water freezes into ice.
Condensed matter theorists have recently made major strides in understanding the pattern behind the different collective behaviors that can arise, with the goal of enumerating and classifying all possible phases of matter.
They’ve also begun to explore the wilderness of phases that can arise near absolute zero in 3-D matter.
Enumerating phases of matter could have been “Like stamp collecting,” Vishwanath said, “Each a little different, and with no connection between the different stamps.” Instead, the classification of phases is “More like a periodic table. There are many elements, but they fall into categories and we can understand the categories.”
While classifying emergent particle behaviors might not seem fundamental, some experts, including Xiao-Gang Wen of the Massachusetts Institute of Technology, say the new rules of emergent phases show how the elementary particles themselves might arise from an underlying network of entangled bits of quantum information, which Wen calls the “Qubit ocean.” For example, a phase called a “String-net liquid” that can emerge in a three-dimensional system of qubits has excitations that look like all the known elementary particles.
Before these zero-temperature phases cropped up, physicists thought they had phases all figured out.