Scientists find anyons in one-dimensional quantum system

Anyons can now exist in one dimension

Scientists have discovered a way for anyons, a strange type of quantum particle, to exist in a one-dimensional system. This expands the known "third kingdom" of particles beyond the traditional boson and fermion categories.

The research was conducted by teams from the Okinawa Institute of Science and Technology and the University of Oklahoma. Their findings are detailed in two separate papers published in the journal Physical Review A.

The quantum particle rulebook

All particles in our three-dimensional universe are classified as either bosons or fermions. This classification is defined by a quantum property called spin.

Bosons, like photons, have integer spin. Fermions, like electrons, have half-integer spin. A critical rule is that two fermions cannot occupy the same quantum state, which is why solid matter exists.

• Bosons: Photons, gluons, Higgs boson. Integer spin.
• Fermions: Electrons, protons, neutrons. Half-integer spin.

Anyons defy this binary. They were first theorized half a century ago and experimentally observed in 2020, but only in two-dimensional materials.

Breaking the rules in lower dimensions

Anyons can only exist in lower-dimensional spaces because particles there have restricted movement. In 3D, when two identical particles swap places, the math governing the exchange is simple: the result squared must equal 1.

This forces particles to be either fermions (-1) or bosons (1). In two dimensions, the math allows for a continuous range of values between -1 and 1. Particles in that range are anyons.

"To satisfy the law of indistinguishability, we need exchange factors over a continuous range," said Raúl Hidalgo-Sacoton, a Ph.D. student at OIST and study co-author.

A recipe for adjustable anyons

The new research proves this boson-fermion binary is also broken in one dimension. The team not only identified the possibility of one-dimensional anyons but also found a method to tune their quantum statistics.

In one dimension, particles cannot avoid each other; they must pass through one another. This interaction changes the exchange factor, a property likely connected to the strength of the short-range forces between particles.

"We’ve identified not only the possibility of existence of one-dimensional anyons, but we’ve also shown how their exchange statistics can be mapped," said Thomas Busch, a co-author from OIST.

Opening a door to new physics

The discovery opens a new frontier for exploring fundamental quantum mechanics. It allows scientists to probe a wider spectrum of particle behaviors that are impossible in our everyday 3D world.

"Every particle in our universe seems to fit strictly into two categories: bosonic or fermionic. Why are there no others?" Busch said. "With these works, we’ve now opened the door to improving our understanding of the fundamental properties of the quantum world."

The researchers express excitement about where this theoretical and experimental path will lead, suggesting it could reveal new truths about the fabric of our universe.