Most people are familiar with the four traditional states of matter: solid, liquid, gas and plasma. However, scientists have logged over 20 additional “exotic” states of matter, and a new one was recently added to the list. The newly discovered state of matter, called a “quantum spin liquid,” breaks electrons – which were previously, as fundamental particles, considered indivisible – into pieces.
In the case of a quantum spin liquid, neither “spin” nor “liquid” take on their obvious meanings. In quantum mechanics, spin does not denote that a particle is rotating, but rather serves as a metaphor for strange properties of quantum particles. When an electrically charged particle, like an electron, rotates, it creates a magnetic field. However, electrons have much stronger magnetic fields than could ever be accounted for by any realistic speed of rotation. Quantum spin accounts for the rest of a particle’s magnetic field that could not be accounted for by the particle actually spinning, but it is an intrinsic property, not an action (like rotation) the particle is performing. The word “liquid” serves as a metaphor: just as water is primarily made of disordered ice molecules, quantum spin liquids are essentially a more disordered version of regular magnetic particles.
The existence of quantum spin liquids was predicted 40 years ago due to the behavior of certain magnetic materials, but they had yet to be directly observed. “Until recently, we didn’t even know what the experimental fingerprints of a quantum spin liquid would look like,” said paper co-author Dr. Dmitry Kovrizhin. “One thing we’ve done in previous work is to ask, if I were performing experiments on a possible quantum spin liquid, what would I observe?”
What scientists at the University of Cambridge in England and the Oak Ridge National Laboratory in Tennessee did observe were particles called Majorana fermions, created when
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