June 15, 2018 (Phys.org) -- An undiscovered type of matter, called "up down quark matter," may exist just beyond the end of the current periodic table and has potential as a new source of energy.
Currently, the heaviest element on the periodic table is oganesson, which has an atomic mass of 294 and was officially named in 2016. Like every element on the periodic table, nearly all of oganesson's mass comes from protons and neutrons (types of baryons) that are themselves made of three quarks each. A crucial feature of all known baryonic matter is that its quarks are bound together so tightly by the strong force that they are inseparable. As particles made of bound quarks (such as protons and neutrons) are called hadrons, scientists refer to the ground state of baryonic matter as "hadronic matter."
But oganesson may be one of the last of its kind. In a new paper, scientists predict that elements with masses greater than approximately 300 may be composed of freely flowing "up" and "down" quarks -- the same kind that protons and neutrons are made of, but these quarks wouldn't be bound into triplets. The scientists predict that this type of matter, called "up down quark matter," or udQM, would be stable for extremely heavy elements that might exist just beyond the end of the current periodic table. If it could be produced on Earth, quark matter has the potential to be used as a new source of energy.
The possibility that heavy baryonic matter has a udQM ground state rather than a hadronic one is described in a paper published in Physical Review Letters by University of Toronto physicists Bob Holdom, Jing Ren, and Chen Zhang.
The idea that some kind of quark matter might form the ground state of baryonic matter is not new. In a famous paper from 1984, physicist Edward Witten suggested that strange quark matter (SQM) might fulfill this role. However, SQM consists of comparable amounts of up, down, and strange quarks. One of the new results of the latest study is that quark matter without strange quarks, i.e., udQM, has lower bulk energy per baryon than either SQM or hadronic matter, making it energetically favorable.
"Physicists have been searching for SQM for decades," the researchers told Phys.org. "From our results, many searches may have been looking in the wrong place. ... It is quite a basic question to answer: What is the lowest energy state of a sufficiently large number of quarks? We argue that the answer is not nuclear matter or strange SQM, but rather udQM, a state composed of nearly massless up and down quarks."