Scientists have discovered a novel pathway to create materials that exhibit complex ‘disordered’ magnetic properties at the quantum level. This newly developed material, which is built around a framework of ruthenium, meets the criteria for the elusive ‘Kitaev quantum spin liquid state’—a phenomenon that researchers have been striving to comprehend for many years.
For the first time, scientists have introduced a new method to synthesize materials showcasing complex ‘disordered’ magnetic traits at the quantum level. This particular material, based on a ruthenium framework, meets the criteria for the ‘Kitaev quantum spin liquid state,’ an enigmatic phenomenon that has puzzled scientists for decades.
Published in Nature Communications, this study conducted by researchers from the University of Birmingham represents a significant advancement toward creating and controlling quantum materials with innovative properties that diverge from classical physics principles.
Importantly, these materials offer a different approach to magnetic properties compared to traditional ‘ferromagnets’, which are organized around two poles. Ferromagnets—such as the common fridge magnets—contain electrons that interact with one another, each acting as a tiny magnet that attracts or repels, aligning in the same direction, which generates the magnet’s force.
In contrast, quantum spin liquid materials display magnetic properties that do not follow this pattern. Instead of the well-organized traits typical of ferromagnets, these materials are disordered, and the electrons within them connect magnetically through a phenomenon called quantum entanglement.
Although quantum spin liquids are theoretically acknowledged and have been modeled by scientists, creating them in a laboratory setting or finding them naturally occurring has not been previously achievable.
The latest research describes the properties of a unique ruthenium-based material that paves the way for investigating these states of matter.
Dr. Lucy Clark, the lead researcher, states: “This work represents a crucial step in learning how to design new materials that let us explore quantum states of matter. It unveils a vast array of materials that remain largely unexamined and could provide significant insights into engineering new magnetic properties for quantum applications.”
Although there are several natural copper minerals and crystalline structures where scientists suspect the quantum spin liquid state may exist, these have yet to be verified due to the added structural complexities found in nature. The complicated nature of quantum spin liquids also challenges theorists, as modeling leads to numerous conflicting magnetic interactions that are hard to decipher, causing disagreements among physicists.
A model created by theoretical physicist Alexei Kitaev in 2009 laid out some fundamental principles for quantum spin liquids, but the magnetic interactions it described necessitated an environment that scientists have been unable to produce in practice without the materials reverting to a standard ordered magnetic state.
This behavior is believed to be linked to the tightly packed crystal structures of potential materials. The ions in these structures are so closely arranged that they can directly interact, leading to a return to magnetic order.
Using specialized instruments at the UK’s ISIS Neutron and Muon Source, along with the Diamond Light Source, the Birmingham team demonstrated that a new material featuring an open framework structure can adjust the interactions between the ruthenium metal ions, creating a new pathway to the Kitaev quantum spin liquid state.
Crucially, the magnetic interactions within these more open structures are weaker than they would otherwise be, allowing scientists more flexibility to modify their specific behaviors.
“While this research hasn’t produced an ideal Kitaev material, it has established a valuable link between theoretical work in this field and experimentation, and opened up promising new research avenues,” concluded Dr. Clark.
