February 26, 2024

A new state of matter with chiral properties

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ARPES resolved by CP spin. TheEDCs obtained at six selected time points (±kIwhere I = 1, 2 or 3) with fixed spins and circular polarizations. In particular, the orange curves are obtained by measuring the EDCs at positive values k values, right circularly polarized light and spin-up channel (W+(k↑)), while the green curves are obtained with negative k values, left circularly polarized light and spin-down channel (W+(-k↓)). B, ARPES spectra with inverted rotation and circularly polarized light configurations. The orange curves refer to W+(-k↑), while the green curves are obtained for W(k↓). wARPES image indicating the k values ​​at which EDCs were taken. Note that the settings in The It is B show a difference that is greater than the experimental uncertainty. dThe amplitudes of circular dichroism (in k summarized to see the actual residue) are reported for integrated and spin-resolved measurements. The data shows that the spin integrated signal (gray curve) shows a finite value as large as 10% (which is also similar to the experimental uncertainty of 8% as shown in ref. 39), but the spin-resolved channels show a notably larger amplitude, by a factor of 2 and 3 for ascending and descending channels, respectively. Amplitude values ​​were extracted from the data shown in The It is B and in Extended Data Fig. 3, after including the Sherman function and calculating the true spin polarization, as described in Methods. The other nominee k points, as well as the dichroic amplitude in terms of the momentum distribution curve, are shown in the Extended Data Figures. 4 and 5, and corroborate the validity of our result. Credit: Nature (2024). DOI: 10.1038/s41586-024-07033-8

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ARPES resolved by CP spin. TheEDCs obtained at six selected time points (±kIwhere I= 1, 2 or 3) with fixed spins and circular polarizations. In particular, the orange curves are obtained by measuring the EDCs at positive values k values, right circularly polarized light and spin-up channel (W+(k↑)), while the green curves are obtained with negative k values, left circularly polarized light and spin-down channel (W+(-k↓)). B, ARPES spectra with inverted rotation and circularly polarized light configurations. The orange curves refer to W+(-k↑), while the green curves are obtained for W(k↓). wARPES image indicating the k values ​​at which EDCs were taken. Note that the settings in The It is B show a difference that is greater than the experimental uncertainty. dThe amplitudes of circular dichroism (in k summarized to see the actual residue) are reported for spin-integrated and spin-resolved measurements. The data shows that the spin integrated signal (gray curve) shows a finite value as large as 10% (which is also similar to the experimental uncertainty of 8% as shown in ref. 39), but the spin-resolved channels show a notably larger amplitude, by a factor of 2 and 3 for ascending and descending channels, respectively. Amplitude values ​​were extracted from the data shown in The It is B and in Extended Data Fig. 3, after including the Sherman function and calculating the true spin polarization, as described in Methods. The other nominee k points, as well as the dichroic amplitude in terms of the momentum distribution curve, are shown in the Extended Data Figures. 4 and 5, and corroborate the validity of our result. Credit: Nature (2024). DOI: 10.1038/s41586-024-07033-8

An international research group has discovered a new state of matter characterized by the existence of a quantum phenomenon called chiral current. These currents are generated on an atomic scale by a cooperative movement of electrons, unlike conventional magnetic materials whose properties originate from the quantum characteristic of an electron known as spin and its ordering in the crystal.

Chirality is an extremely important property in science, for example, it is also fundamental to understanding DNA. In the discovered quantum phenomenon, the chirality of currents was detected through the study of the interaction between light and matter, in which a properly polarized photon can emit an electron from the surface of the material with a well-defined spin state.

The discovery, published in Naturesignificantly enriches our knowledge of quantum materials in the search for chiral quantum phases and the phenomena that occur on the surface of materials.

“The discovery of the existence of these quantum states could pave the way for the development of a new type of electronics that employs chiral currents as information carriers in place of the electron charge”, explains Federico Mazzola, researcher in Condensed Matter Physics at Ca.’ Foscari University of Venice and leader of the research.

“Furthermore, these phenomena could have an important implication for future applications based on new chiral optoelectronic devices, and a major impact on the field of quantum technologies for new sensors, as well as the biomedical and renewable energy fields.”

Born from a theoretical prediction, this study directly and for the first time verified the existence of this quantum state, until now enigmatic and elusive, thanks to the use of the Italian Elettra synchrotron. Until now, knowledge about the existence of this phenomenon was, in fact, limited to theoretical predictions for some materials. Its observation on the surfaces of solids makes it extremely interesting for the development of new ultrathin electronic devices.

The research group, which includes national and international partners, including the Ca’ Foscari University of Venice, the Spin Institute, the CNR Materials Officina Institute and the University of Salerno, investigated the phenomenon of a material already known to the scientific community for its properties electronics. and for superconducting spintronics applications, but the new discovery has a broader scope, being much more general and applicable to a wide range of quantum materials.

These materials are revolutionizing quantum physics and the current development of new technologies, with properties that go far beyond those described by classical physics.

More information:
Federico Mazzola, Signatures of a surface spin-orbital chiral metal, Nature(2024). DOI: 10.1038/s41586-024-07033-8. www.nature.com/articles/s41586-024-07033-8

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