Theoretical quantum spin liquid prepared for the first time

Theoretical quantum spin liquid prepared for the first time
The muon spin spectrometer used in the study at the Paul Scherrer Institute. The sample being studied is placed in the cryostat located in the middle, and a muon beam is aimed at it from the back left direction. Credit: Otto Mustonen

In 1987, Paul W. Anderson, a Nobel Prize winner in physics, proposed that high-temperature superconductivity, or loss of electrical resistance, is related to an exotic quantum state now known as quantum spin liquid. Magnetic materials are made up of very tiny magnets, which can be as small as individual electrons. The strength and direction of these are described by the magnetic moment. In quantum spin liquids, magnetic moments behave like a liquid and do not freeze or order even at absolute zero. These quantum states are being studied as promising materials for new, so-called topological quantum computers, in which operations are based on particle-like excited states found in quantum spin liquids. In addition to large computational power, a topological quantum computer is characterised by high fault tolerance, which makes it possible to increase the size of the computer. However, only a few quantum spin liquids suitable for topological quantum computers have been identified so far.

Now, for the first time ever, researchers from Aalto University, Brazilian Center for Research in Physics (CBPF), Technical University of Braunschweig and Nagoya University have produced the superconductor-like liquid predicted by Anderson. This is an important step towards understanding superconductors and . The preparation of a quantum spin liquid was made possible by a new way of tailoring the properties of that was developed by chemists at Aalto University. The results of the research have been published in Nature Communications.

High-temperature superconductors are copper oxides in which the copper ions form a square lattice so that the adjacent face in opposite directions. When this structure is disturbed by changing the oxidation state of copper, the material becomes superconducting. In the new research now published, the magnetic interactions of this square structure were modified with ions with a d10 and d0 electronic structure, which turned the material into a .

Theoretical quantum spin liquid prepared for the first time
The magnetically ordered square lattice of copper ions. Tailoring the structure caused the formation of quantum spin liquid. Modifying the structure in a different way results in high-temperature superconductivity. Credit: Otto Mustonen
"In the future, this new d10/d0 method can be utilised in many other magnetic materials, including various quantum materials," says Doctoral Candidate Otto Mustonen from Aalto University.

Seamless cooperation

Empirical detection of quantum spin liquids is difficult and requires extensive research infrastructure.

"We used muon spin spectroscopy in the this study. This method is based on the interaction of very short-lived, electron-like elementary particles, known as muons, with the material being studied. The method can detect very weak magnetic fields in quantum materials," says Professor F. Jochen Litterst from the Technical University of Braunschweig. The measurements were performed at the Paul Scherrer Institute in Switzerland.

"In addition to top-class equipment, the research requires seamless cooperation between chemists and physicists," says Professor Maarit Karppinen. "We're going to need the same international multidisciplinary approach in the future so that this research on quantum spin liquids can lead us to the experimental realization of the topological quantum computer."


Explore further

Stirring up a quantum spin-liquid with disorder

More information: O. Mustonen et al. Spin-liquid-like state in a spin-1/2 square-lattice antiferromagnet perovskite induced by d10–d0 cation mixing, Nature Communications (2018). DOI: 10.1038/s41467-018-03435-1
Journal information: Nature Communications

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Citation: Theoretical quantum spin liquid prepared for the first time (2018, March 15) retrieved 21 May 2019 from https://phys.org/news/2018-03-theoretical-quantum-liquid.html
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Apr 04, 2018
Philip Warren Anderson
Born in 1923 at 94 in Indianapolis you always make tracks round the corner to Cambridge where from 1967 spent 8 glories years as theoretical physicists at Cambridge University. The next step in realising 373K zero resistance conductors is solving the problem the physicist Heinrich Friedrich Emil Lenz in 1834 formulated "Lenz's law" a direction of induced current in a conductor by a changing magnetic field due to induction creates a magnetic field that opposes the change that produced it. Everyone knows the levitating properties of zero resistance conductors; this property occurs in copper conductors it's just harder to spot. Drop a tube of aluminium in a magnetic field slow the aluminium's velocity which is "Lenz's law", in conductors and zero resistance conductors Lenz law repels the electrons to the circumference increasing resistance making copper glow hot and cancels zero resistance in zero resistance conductors

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