Quantum materials: Electron spin measured for the first time – EurekAlert

image:Three perspectives of the surface on which the electrons move. On the left, the experimental result, in the center and on the right the theoretical modeling. The red and blue colors represent a measure of the speed of the electrons. Both theory and experiment reflect the symmetry of the crystal, very similar to the texture of traditional Japanese "kagome" baskets view more

Credit: University of Bologna

An international research team has succeededfor the first timein measuring the electron spin in matter- i.e., the curvature of space in which electrons live and move - within "kagome materials", a new class ofquantum materials.

The results obtained - published inNature Physics- could revolutionise the way quantum materials are studied in the future, opening the door tonew developments in quantum technologies, with possible applications in a variety of technological fields, fromrenewable energytobiomedicine, fromelectronicstoquantum computers.

Success was achieved by an international collaboration of scientists, in whichDomenico Di Sante, professor at theDepartment of Physics and Astronomy "Augusto Righi", participated for theUniversity of Bolognaas part of his Marie CurieBITMAPresearch project. He was joined by colleagues from CNR-IOM Trieste, Ca' Foscari University of Venice, University of Milan, University of Wrzburg (Germany), University of St. Andrews (UK), Boston College and University of Santa Barbara (USA).

Through advanced experimental techniques, usinglight generated by a particle accelerator, theSynchrotron, and thanks tomodern techniques for modelling the behaviour of matter, the scholarswere able to measure electron spin for the first time, related to the concept oftopology.

"If we take two objects such as a football and a doughnut, we notice thattheir specific shapesdeterminedifferent topological properties, for example because the doughnut has a hole, while the football does not,"Domenico Di Santeexplains. "Similarly, the behaviour of electrons in materials is influenced by certain quantum propertiesthat determine their spinning in the matter in which they are found, similar to how the trajectory of light in the universe is modified by the presence of stars, black holes, dark matter, and dark energy, which bend time and space."

Although this characteristic of electrons has been known for many years, no one had until now been able to measure this "topological spin" directly. To achieve this, the researchers exploited a particular effect known as "circular dichroism": a special experimental technique that can only be used with a synchrotron source, which exploits the ability of materialsto absorb light differentlydependingon their polarisation.

Scholars have especially focused on "kagome materials", a class of quantum materials that owe their name to their resemblance to the weave of interwoven bamboo threads that make up a traditional Japanese basket (called, indeed, "kagome").These materials are revolutionising quantum physics, and the results obtained could help us learn more about their special magnetic, topological, and superconducting properties.

"These important results were possible thanks toa strong synergy between experimental practice and theoretical analysis," addsDi Sante. "The team's theoretical researchers employedsophisticated quantum simulations, only possible with the use of powerful supercomputers, and in this way guided their experimental colleagues to the specific area of the material wherethe circular dichroism effectcould be measured.

The study was publishedinNature Physicswith the title "Flat band separation and robust spin Berry curvature in bilayer kagome metals". The first author of the study isDomenico Di Sante, a researcher at the"Augusto Righi" Department of Physics and Astronomyof theUniversity of Bologna. He worked with scholars from the CNR-IOM of Trieste, the Ca' Foscari University of Venice, the University of Milan, the University of Wrzburg (Germany), the University of St. Andrews (UK), the Boston College and the University of Santa Barbara (USA).

Flat band separation and robust spin Berry curvature in bilayer kagome metals

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Quantum materials: Electron spin measured for the first time - EurekAlert