Finding order in disorder demonstrates a new state of matter

April 02, 2018

LOS ALAMOS, N.M., April 2, 2018--Physicists have identified a new state of matter whose structural order operates by rules more aligned with quantum mechanics than standard thermodynamic theory. In a classical material called artificial spin ice, which in certain phases appears disordered, the material is actually ordered, but in a "topological" form.

"Our research shows for the first time that classical systems such as artificial spin ice can be designed to demonstrate topological ordered phases, which previously have been found only in quantum conditions," said Los Alamos National Laboratory physicist Cristiano Nisoli, leader of the theoretical group that collaborated with an experimental group at the University of Illinois at Urbana-Champaign, led by Peter Schiffer (now at Yale University).

Physicists generally classify the phases of matter as ordered, such as crystal, and disordered, such as gases, and they do so on the basis of the symmetry of such order, Nisoli said.

"The demonstration that these topological effects can be designed into an artificial spin ice system opens the door to a wide range of possible new studies," Schiffer said.

Specialized material maintained puzzling energy levels in experiments

In the new research, the team explored a particular artificial spin ice geometry, called Shakti spin ice. While these materials are theoretically designed, this time, the discovery of its exotic, out-of-equilibrium properties proceeded from experiments to theory.

Performing photoemission electron microscopy characterization at the U.S. Department of Energy's Advanced Light Source at Lawrence Berkeley National Laboratory, Schiffer's team revealed something puzzling: Unlike other artificial spin ices, which could reach their low-energy state as temperature was reduced in successive quenches, Shakti spin ice stubbornly remained at about the same energy level. "The system gets stuck in a way that it cannot rearrange itself, even though a large-scale rearrangement would allow it to fall to a lower energy state," Schiffer said.

Clearly, something was being conserved, but nothing appeared as an obvious candidate in a material artificially devised to provide a disordered spin picture.

Backing off to see the big picture

Moving away from a spin picture and concentrating on an emergent description of the excitations of the system, Nisoli described a low-energy state that could be mapped exactly into a celebrated theoretical model, the "dimer cover model," whose topological properties had been recognized before. Then, data from the experiment confirmed topological charge conservation and thus a long lifetime for the excitations.

"I find it most intriguing because usually theoretical frameworks move from classical physics to quantum physics. Not so with topological order," Nisoli said.

Collaborative success

Physical experiments were performed by Schiffer's team at the University of Illinois at Urbana-Champaign and were funded by the U.S. Department of Energy's Office of Science. The kinetics of the material were investigated in real time and real space at the Advanced Light Source.
The theoretical work of Nisoli was funded by a Laboratory Directed Research and Development (LDRD) grant from Los Alamos National Laboratory, and the work of Caravelli by LDRD though the Oppenheimer Distinguished Fellowship at Los Alamos.

Publication: Classical Topological Order in the Kinetics of Artificial Spin Ice, Nature Physics, DOI: 10.1038/s41567-018-0077-0

About Los Alamos National Laboratory

Los Alamos National Laboratory, a multidisciplinary research institution engaged in strategic science on behalf of national security, is operated by Los Alamos National Security, LLC, a team composed of Bechtel National, the University of California, BWX Technologies, Inc. and URS Corporation for the Department of Energy's National Nuclear Security Administration.

Los Alamos enhances national security by ensuring the safety and reliability of the U.S. nuclear stockpile, developing technologies to reduce threats from weapons of mass destruction, and solving problems related to energy, environment, infrastructure, health and global security concerns.

DOE/Los Alamos National Laboratory

Related Quantum Mechanics Articles from Brightsurf:

Theoreticians show which quantum systems are suitable for quantum simulations
A joint research group led by Prof. Jens Eisert of Freie Universit├Ąt Berlin and Helmholtz-Zentrum Berlin (HZB) has shown a way to simulate the quantum physical properties of complex solid state systems.

A new interpretation of quantum mechanics suggests reality does not depend on the measurer
For 100 years scientists have disagreed on how to interpret quantum mechanics.

New evidence for quantum fluctuations near a quantum critical point in a superconductor
A study has found evidence for quantum fluctuations near a quantum critical point in a superconductor.

Simulating quantum 'time travel' disproves butterfly effect in quantum realm
Using a quantum computer to simulate time travel, researchers have demonstrated that, in the quantum realm, there is no 'butterfly effect.' In the research, information--qubits, or quantum bits--'time travel' into the simulated past.

Orbital engineering of quantum confinement in high-Al-content AlGaN quantum well
Recently, professor Kang's group focus on the limitation of quantum confine band offset model, the hole states delocalization in high-Al-content AlGaN quantum well are understood in terms of orbital intercoupling.

A Metal-like Quantum Gas: A pathbreaking platform for quantum simulation
Coherent and ultrafast laser excitation creates an exotic matter phase with spatially overlapping electronic wave-functions under nanometric control in an artificial micro-crystal of ultracold atoms.

Fluid mechanics mystery solved
An environmental engineering professor has solved a decades-old mystery regarding the behavior of fluids, a field of study with widespread medical, industrial and environmental applications.

Quantum leap: Photon discovery is a major step toward at-scale quantum technologies
A team of physicists at the University of Bristol has developed the first integrated photon source with the potential to deliver large-scale quantum photonics.

USTC realizes the first quantum-entangling-measurements-enhanced quantum orienteering
Researchers enhanced the performance of quantum orienteering with entangling measurements via photonic quantum walks.

A convex-optimization-based quantum process tomography method for reconstructing quantum channels
Researchers from SJTU have developed a convex-optimization-based quantum process tomography method for reconstructing quantum channels, and have shown the validity to seawater channels and general channels, enabling a more precise and robust estimation of the elements of the process matrix with less demands on preliminary resources.

Read More: Quantum Mechanics News and Quantum Mechanics Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to