​​​​​​​Computational sleuthing confirms first 3D quantum spin liquid | Rice News | News and Media Relations
A 3D representation of the spin-excitation continuum—a possible hallmark of a quantum spin liquid—observed in 2019 in a single crystal sample of cerium zirconium pyrochlore. Credit: Tong Chen/Rice University

Computational detective work by U.S. and German physicists has shown that cerium is a quantum spin liquid.

Despite the name, quantum spin liquids are solid materials in which quantum entanglement and the geometric arrangement of atoms frustrate the natural tendency of electrons to magnetically order themselves in relation to one another. The quantum spin liquid has a geometric frustration that makes it hard for electrons to move between magnetic states.

Finding convincing evidence that quantum spin liquids exist in actual physical materials has been a decades-long challenge for theoretical physicists. A number of 2D or 3D materials have been proposed as possible quantum spin liquids, but there is no consensus among physicists.

In the open-access journal npj Quantum Materials, he and colleagues from Rice, Florida State University and the Max Planck Institute for Physics of Complex Systems in Dresden, Germany, published their work.

The work confirms that the single crystals of the cerium pyrochlore are quantum spin liquids.

Spin is the property of electrons that leads to magnetism. When measured, individual electron spins always point up or down, and each electron behaves like a tiny bar magnet with a north and south pole. Most everyday materials have spins point up or down. electrons are anti-social and this can cause them to arrange their spins in relation to their neighbors In magnets and antiferromagnets, the spins are arranged in a pattern.

At very low temperatures, quantum effects become more prominent, and this causes electrons to arrange their spins in most materials, even those where spins would point in random directions at room temperature. No matter how cold the material becomes, quantum spin liquids do not point in a definite direction.

A quantum spin liquid is an example of a fractionalized state of matter and is an example of the Rice Center for Quantum Materials. They are strange, delocalized objects that carry half of a degree of freedom. It is like half of a spin.

The first evidence of a quantum spin liquid was found in a study led by Rice experimental physicist. The team's samples were the first of their kind because of their 2-to-7 ratio of cerium, zirconium and oxygen, and single crystals. A continuum of spin excitations measured at temperatures as low as 35 millikelvin was revealed by inelastic neutron scattering experiments by Dai and colleagues.

The study was to prove to the jury that the suspect is guilty.

State-of-the-art Monte Carlo methods, exact diagonalization and analytical tools were used to build their case. The Monte Carlo simulations were performed by Anish Bhardwaj and Hitesh Changlani, with contributions from Rice and Florida State.

The exact parameters of which there are at least four were not known. We wanted to find the values for cerium pyrochlore and see if they describe a quantum spin liquid.

​​​​​​​Computational sleuthing confirms first 3D quantum spin liquid | Rice News | News and Media Relations
U.S. and German physicists found evidence that cerium zirconium pyrochlore crystals are “octupolar quantum spin liquids” in which octupolar magnetic moments (red and blue) contribute to fractionalized magnetism. Credit: A. Nevidomskyy/Rice University

He said that it would be similar to a ballistics expert who is usingNewton's second law to calculate a bullet's trajectory. The initial conditions are similar to the parameters. We had to reverse engineer or sleuth out to find out what the initial conditions were in this material.

The model was tested against the results of previous studies of cerium zirconium pyrochlore.

If you only have one piece of evidence, you may find other models that fit the description. A single candidate had to match all three experiments.

The same type of quantum magnetic fluctuations that occur in quantum spin liquids are implicated in some studies. Computational findings are primarily of interest to physicists.

He said that it satisfied his innate desire to find out how nature works. It is not tied to quantum computing, although there are ideas for using fractionalized excitations as a platform for logical qubits.

The connection between quantum spin liquids and magnetic monopoles, theoretical particles whose potential existence is still debated, is an interesting point for physicists.

When people talk about fractionalization, they mean that the system behaves like an electron splitting into two halves, and then merging somewhere later.

Magnetic monopoles can be visualized as isolated magnetic poles, like the upward or downward facing pole of a single electron.

The north and south monopoles always come in pairs. Magnetic monopoles can hypothetically exist, and quantum theorists constructed these almost 100 years ago to explore fundamental questions about quantum mechanics.

Magnetic monopoles do not exist in a raw form in our universe. Two fractionalized quasiparticles called spinons are created by a single spin flip.

There was evidence that spinons were created in an unusual way. The study suggests that the magnetic atoms in the pyrochlore have spin-like magnetic quasiparticles with eight poles. The material was produced from both octupolar sources and more conventional, dipolar spin moments.

The exact proportions of interactions of these two components were established by our modeling.

More information: Anish Bhardwaj et al, Sleuthing out exotic quantum spin liquidity in the pyrochlore magnet Ce2Zr2O7, npj Quantum Materials (2022). DOI: 10.1038/s41535-022-00458-2 Citation: Computational sleuthing confirms first 3D quantum spin liquid (2022, May 10) retrieved 10 May 2022 from https://phys.org/news/2022-05-sleuthing-3d-quantum-liquid.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.