Stirring up a quantum spin-liquid with disorder

December 13, 2017, US Department of Energy
An elusive state of matter—quantum spin liquid—may actually be enhanced rather than suppressed by disorder as seen in a compound that contains praseodymium, zirconium, and oxygen (Pr2Zr2O7). In this material, the praseodymium ions with magnetic moments (green arrows in right image) occupy a lattice of corner-sharing tetrahedra. The signature of a quantum spin liquid is the persistence of inelastic neutron scattering intensity for w>0 (left) near absolute zero (temperature). The variation in intensity with increasing magnetic field (bottom to top) indicates that a weak disorder can prevent spin freezing and promote a quantum spin liquid state. Credit: US Department of Energy

Disorder is generally thought to be detrimental to creating materials with unusual magnetism or other quantum phenomena. However, a team found that weak disorder surprisingly stabilizes a rare quantum state called a quantum spin liquid. In this state, fluctuations of electronic spins persist all the way to temperatures near absolute zero. The particular material is made of praseodymium, zirconium, and oxygen (Pr2Zr2O7). The material contains rare earth ions (Pr3+) with an even number of electrons on a weakly disordered crystalline lattice. While the crystalline lattice frustrates conventional magnetism, weak disorder promotes the rare quantum spin liquid state.

The discovery that weak disorder can induce this rare state opens a new direction in the quest for a practical spin liquid. This state of matter could be useful as building blocks for quantum computers. These computers could be orders of magnitude faster than today's computers. This speed translates into computational power to solve problems that can't be feasibly solved today.

A rare state of matter called a quantum spin liquid proposed over 40 years ago is being pursued for its unique physical properties. In a quantum spin liquid, electronic spins do not form a static ordered pattern as in conventional magnetic , but fluctuate in a coordinated (entangled) fashion even at extremely low temperatures. But can such quantum fluctuating states of matter exist in practical materials which are inevitably disordered and can quantitative information about them be extracted from neutron scattering experiments?

Towards addressing such questions, a team of researchers led by Johns Hopkins University studied a pyrochlore oxide with the chemical formula Pr2Zr2O7. Conventional magnetism is frustrated by the geometry of the pyrochlore lattice when magnetic ions occupy a specific location in the crystal lattice and this can lead to exotic magnetic states. Combining solid-state synthesis, high-quality single crystal growth, and advanced neutron scattering, this research unveiled the presence of a quantum spin liquid in Pr2Zr2O7.

The inelastic neutron scattering data show the signature for this rare state where a band of (inelastic, w>0) scattering intensity persists at temperatures close to . This research points to a new paradigm that at appropriate levels, weak structural disorder may actually promote the formation of a quantum spin liquid with entangled electronic spins. This ability to manipulate and induce quantum magnetism in spite of disorder could pave the way for new and more practical materials with the elusive liquid for applications including quantum computing.

Explore further: Neutrons reveal suppression of magnetic order in pursuit of a quantum spin liquid

More information: J.-J. Wen et al. Disordered Route to the Coulomb Quantum Spin Liquid: Random Transverse Fields on Spin Ice inPr2Zr2O7, Physical Review Letters (2017). DOI: 10.1103/PhysRevLett.118.107206

Related Stories

Monopole current offers way to control magnets

November 13, 2017

In work published in Physical Review Letters, scientists from RIKEN in Japan have discovered interesting new magnetic properties of a type of materials known as "quantum spin ice." These materials demonstrate interesting ...

Novel state of matter: Observation of a quantum spin liquid

July 26, 2016

A novel and rare state of matter known as a quantum spin liquid has been empirically demonstrated in a monocrystal of the compound calcium-chromium oxide by team at HZB. According to conventional understanding, a quantum ...

Recommended for you

Tangled magnetic fields power cosmic particle accelerators

December 13, 2018

Magnetic field lines tangled like spaghetti in a bowl might be behind the most powerful particle accelerators in the universe. That's the result of a new computational study by researchers from the Department of Energy's ...

Stretched quantum magnetism uncovered by quantum simulation

December 13, 2018

By studying ultracold atoms trapped in artificial crystals of light, Guillaume Salomon, a postdoc at the Max-Planck-Institute of Quantum Optics and a team of scientists have been able to directly observe a fundamental effect ...

The secret life of cloud droplets

December 13, 2018

Do water droplets cluster inside clouds? Researchers confirm two decades of theory with an airborne imaging instrument.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.