NASA/JPL-Caltech
Things change in lower dimensions. A new type of quasiparticles in one-dimensional systems could broaden the conceptual framework of particle physics and quantum matter.
In two studies published in December in Physical Review A ( and ), researchers from Okinawa Institute of Science and Technology (OIST) and the University of Oklahoma present a theoretical model for the existence of “anions” (negatively charged ion) adjustable in one dimension and analyze its properties, opening a new avenue to explore quantum statistics beyond the classical division between fermions and bosons.
In particle physics in three dimensions, the elementary constituents of matter are generally organized into two groups, explains . Bosons (such as photons and gluons) have integer spin and can occupy the same quantum state, while fermions (such as electrons and neutrinos) have half-integer spin and obey the same quantum state. Pauli exclusion principlewhich prevents two identical fermions from sharing the same state. It is an essential behavior for the structure of matter.
But, in lower dimensions, this separation is no longer absolute. For decades, theory has predicted the existence of anions in two dimensions: quasiparticles whose statistical properties are “between” those of bosons and fermions. The term was popularized by the American physicist Frank Wilczekwho described these objects as belonging to a quantum “third kingdom”. In 2020, the experimental observation of an anion in atomic-thick semiconductors was presented as a historic milestone in science.
The new work goes further, arguing that this “third way” can also manifest itself in one dimension. According to the authors, the key lies in the way particles can change position. In three dimensions, when two identical particles are exchanged, the mathematical factor associated with this exchange must satisfy a simple rule: its square is equal to 1, which restricts the result to two possibilities, corresponding to fermions (−1) or bosons (+1).
In two dimensions, possible trajectories for exchange can include “turns” and “twists,” allowing for exchange factors across a continuum — and that’s where anions emerge.
In the one-dimensional case, the researchers explain, mobility is even more limited: to change places, the particles have to “cross each other”, and this dynamic can break the boson–fermion dichotomy again.
The proposed model also suggests a way to adjust (“tune”) the exchange factor, possibly linked to the intensity of short-range interactions.
Although these are theoretical results, the authors argue that the possibility of mapping and controlling these statistics in one dimension could guide future experiments and deepen understanding of the foundations of quantum behavior.
