For example: physics traditionally tells us that all particles can be classified into one of two types, either bosons or fermions, depending on their properties and behavior. But math says that’s not the whole story – at least, according to a new study.

From the early days of quantum mechanics, scientists have thought that all particles can be categorized into one of two groups—bosons or fermions—based on their behavior.

There is one notable exception to this strict rule of quantum-state segregation. Restricted to just two dimensions, some materials can give rise to a particle-like behavior that breaks the statistical laws expected of fermions and bosons, effectively allowing a unique swapping of quantum states.

“Paraparticles introduce a new kind of symmetry and exclusion principle,” the authors write. These particles obey rules that give rise to exotic thermodynamic behaviors. For instance, they exhibit “generalized exclusion statistics,” determining how many particles can occupy a given quantum state.