2023-07-15 20:10:00
The web of scientific discoveries has once once more expanded, shedding light on a complex aspect of topological quantum materials. This achievement, orchestrated by a team of international scientists, might open new avenues for energy-efficient electronics and cutting-edge technology of the future.
Topological quantum materials are considered to hold hope for more efficient electronics and advanced technologies. One of their remarkable characteristics is their ability to conduct spin-polarized electrons on their surface, although they are non-conductive inside.
To distinguish topological materials from classical materials, scientists usually studied their surface currents. However, the topology of an electron is intimately linked to its quantum wave properties and spin. This relationship has now been directly demonstrated through the photoelectric effect, a phenomenon where electrons are released from a material using light.
Visualize electron topology with “3D glasses”
Professor Giorgio Sangiovanni, founding member of ct.qmat in Würzburg and one of the project’s theoretical physicists, likened the discovery to using 3D glasses to visualize electron topology. He explains : “Electrons and photons can be quantum described as both waves and particles. Therefore, the electrons have a spin that we can measure through the photoelectric effect.”
To do this, the team used circularly polarized X-ray light, light particles possessing a couple. Pr. Sangiovanni specifies: “When a photon encounters an electron, the signal coming from the quantum material depends on the right or left polarization of the photon. In other words, the spin orientation of the electron determines the relative signal strength between left and right polarized beams. Thus, this experience can be thought of as polarized glasses in a 3D cinema, where light beams of different orientations are also used. Our ‘3D glasses’ make electron topology visible.”
Quantum materials, particle accelerator and supercomputer
The success of this research required three years of intense work for the researchers. Their starting point was metal kagome TbV6Sn6, a quantum material.
In this special category of materials, the atomic lattice features a mixture of triangular and hexagonal lattices in a structure reminiscent of a Japanese basket weave. Kagome metals play an important role in ct.qmat’s materials research.
“Before our experimental colleagues might start the synchrotron experiment, we had to simulate the results to make sure we were on the right track. In a first step, we designed theoretical models and performed calculations on a supercomputer,” explains Dr. Domenico di Sante, project leader and theoretical physicist.
The results of the measurements agreed perfectly with the theoretical predictions, allowing the team to visualize and confirm the topology of the kagome metals.
An international research network
The research project involved scientists from Italy (Bologna, Milan, Trieste, Venice), the United Kingdom (St. Andrews), the United States (Boston, Santa Barbara), and Würzburg.
The supercomputer used for the simulations is located in Munich, and the synchrotron experiments were carried out in Trieste. “These research results perfectly illustrate the remarkable results that theoretical and experimental physics can produce when working in tandem,” concludes Professor Sangiovanni.
Synthetic
This worldwide breakthrough in the characterization of topological quantum materials succeeded in demonstrating a new relationship between the topology of electrons and their quantum wave properties. It opens the door to a multitude of possibilities for tomorrow’s electronics and cutting-edge technology.
For a better understanding
What is the photoelectric effect?
The photoelectric effect is a phenomenon that releases electrons from a material, such as metal, using light.
What is a topological quantum material?
A topological quantum material is a type of material that has the ability to conduct spin-polarized electrons on its surface, although it is non-conductive inside.
What is an electron topology?
The topology of an electron is closely related to its quantum wave properties and its spin.
What is the spin of an electron?
The spin of an electron is its intrinsic angular momentum, i.e. the direction in which the particle spins.
What is a supercomputer and why is it used in this type of research?
A supercomputer is a type of computer with high processing capacity, used to perform complex calculations or high-precision simulations. It is used in this type of research to simulate the expected results of an experiment.
What is Kagome Metal?
Kagome metal is a quantum material, in which the atomic lattice presents a mixture of triangular and hexagonal lattices in a structure reminiscent of a Japanese basket weave.
Key illustration caption: Using X-rays (shown in green in the image), researchers created cinematic 3D effects on the metal kagome TbV6Sn6. They have thus succeeded in following the behavior of electrons (blue and yellow in the image) and have taken a step forward in the understanding of quantum materials. (Image: Jörg Bandmann/ct.qmat)
Publication / Flat band separation and robust Berry curvature in Kagome bilayer metals. Domenico Di Sante, Chiara Bigi, Philipp Eck, Stefan Enzner, Armando Consiglio, Ganesh Pokharel, Pietro Carrara, Pasquale Orgiani, Vincent Polewczyk, Jun Fujii, Phil DC King, Ivana Vobornik, Giorgio Rossi, Ilija Zeljkovic, Stephen D. Wilson, Ronny Thomale, Giorgio Sangiovanni, Giancarlo Panaccione and Federico Mazzola. Nature Physics (2023). DOI: 10.5281/zenodo.7787937. https://www.nature.com/articles/s41567-023-02053-z
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