A new discovery led by Princeton University could upend our understanding of how electrons behave under extreme conditions in quantum materials. The finding provides experimental evidence that this familiar building block of matter behaves as if it’s made from two particles: one particle that provides the electron its -ve(negative) charge and another that supplies its magnet-like property, referred to as spin.
“We think this is often the primary hard evidence of spin-charge separation,” said Nai Phuan Ong, Princeton’s Eugene Higgins Professor of Physics and senior author on the paper published within the week in the journal Nature Physics.
The experimental results fulfill a prediction made decades ago to define one among the foremost mind-bending states of matter, the quantum spin liquid. altogether materials, the spin of an electron can point either up or down. within the familiar magnet, all of the spins uniformly point in one direction throughout the sample when the temperature drops below a critical temperature.
However, in spin liquid materials, the spins are unable to determine a consistent pattern even when cooled very on the brink of temperature . Instead, the spins are constantly changing during a tightly coordinated, entangled choreography. The result’s one among the foremost entangled quantum states ever conceived, a state of great interest to researchers within the growing field of quantum computing.
Credit : Peter Czajka, Princeton University
To describe this behavior mathematically, Nobel prize-winning Princeton physicist Anderson (1923-2020), who first predicted the existence of spin liquids in 1973, proposed an explanation: within the quantum regime an electron could also be considered as composed of two particles, one bearing the electron’s -ve (negative) charge and therefore the other containing its spin. Anderson called the spin-containing particle a spinon.
In this new study, the team looked for signs of the spinon during a spin liquid composed of ruthenium and chlorine atoms. At temperatures a fraction of a Kelvin above absolute 0 temperature (or roughly -452 degrees Fahrenheit) and within the presence of a high magnetic flux, ruthenium chloride crystals enter the spin liquid state.
Graduate student Peter Czajka and Tong Gao, Ph.D. 2020, connected three sensitive thermometers to the crystal sitting during a bath maintained at temperatures close to absolute 0 temperature degrees Kelvin. They then applied the magnetic flux and alittle amount of heat to at least one crystal edge to live its thermal conductivity, a quantity that expresses how well it conducts a heat current. If spinons were present, they ought to appear as an oscillating pattern in graph of the thermal conductivity versus magnetic flux .
The oscillating signal they were checking out was tiny — just a couple of hundredths of a degree change — therefore the measurements demanded a very precise control of the sample temperature also as careful calibrations of the thermometers in strong magnetic flux .
The team used the purest crystals available, ones grown at the U.S. Department of Energy’s Oak Ridge National Laboratory (ORNL) under the leadership of David Mandrus, materials science professor at the University of Tennessee-Knoxville, and Stephen Nagler, corporate research fellow in ORNL’s Neutron Scattering Division. The ORNL team has extensively studied the quantum spin liquid properties of ruthenium chloride.
In a series of experiments conducted over nearly three years, Czajka and Gao detected temperature oscillations according to spinons with increasingly higher resolution, providing evidence that the electron consists of two particles according to Anderson’s prediction.
“People are checking out this signature for four decades,” Ong said, “If this finding and therefore the spinon interpretation are validated, it might significantly advance the sector of quantum spin liquids.”
Czajka and Gao spent last summer confirming the experiments while under COVID restrictions that required them to wear masks and maintain social distancing.
“From the purely experimental side,” Czajka said, “it was exciting to ascertain results that in effect break the principles that you simply learn in elementary physics classes.”
This research first reported on Nature Physics.
