The apparent inner calm of quantum materials

The helix structure of BACOVO: the oxygen atoms, represented in red, are organized in octahedra around the cobalt atoms, located at their center. The blue arrows represent the small moments carried by the cobalt atoms, ordered antiferromagnetically along the helical chain. Credit: CEA/CNRS/UGA

Researchers from the University of Geneva (UNIGE) and multi-institutional collaborators have been studying BACOVO—a one-dimensional quantum material. They report that the material exhibits a novel topological phase transition governed by two types of topological excitation. In addition, they were able to choose which of the two types would dominate the other. Their research is published in the journal Nature Physics.

The researchers from CEA, CNRS, and Université Grenoble Alpes were working on a one-dimensional antiferromagnetic material with particular properties: BACOVO (BaCo2V2O8).

“We performed various experiments on BACOVO, an oxide characterized by its helical structure,” the researchers wrote. But the experimental results evidenced a puzzling phase transition—which is why the team called on Thierry Giamarchi, a professor in the Department of Quantum Matter Physics in UNIGE’s Faculty of Science.

Giamarchi says, “Based on their results, we established theoretical frameworks capable of interpreting them. These theoretical models were then tested again using new experiments so they could be validated.”

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