Study investigates pressure-induced superconductor transition in electrons



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Study investigates pressure-induced superconductor transition in electrons

The image on the left shows the atomic structure of the compound Li6P, and to the right the electronic charge density is plotted, where the electronic location in the interstitials can be seen in red. Credit: Zhao et al.

Researchers at Northeast Normal University in China and the University of the Basque Country in Spain recently conducted a study investigating the superconducting transition of electrons. The researchers observed that a stable Li induced pressure6P, identified by the calculations of the swarming structure of first principles, can become a superconductor with a considerably high superconducting transition temperature.


"Considering the vast potential applications of superconducting materials, understanding high-temperature superconductors is a key scientific challenge in condensed matter physics," Aitor Bergara and Guochun Yang, two of the researchers who conducted the study, told Phys.org. the e-mail.

Electrons are ionic compounds in which most electrons reside in the interstitial regions of the crystal and behave like anions. Due to their structural peculiarity, these compounds possess interesting physical properties. For example, the magnitude and distribution of its interstitial electrons can be effectively modulated, either by adjusting their chemical composition or external conditions, such as pressure.

In general, the electrons are very poor superconductors. For example, the experimentally observed superconducting transition temperature of a canonical electret[Here[Here[Ca[Ca24Al28O64]4+ (4e)4 is ~ 0.4 K. On the other hand, it is now well known that under high pressure, alkali metals can easily lose their outer orbital electrons and form electrets.

"Curiously, the pressure-induced lithium electret (Li) is metallic," said Bergara and Yang. "In addition, phosphorus (P) exhibits moderate electronegativity, so that they can trap some electrons in Li-rich Li-P compounds, while the remaining electrons can remain in the interstitial regions.As we are anticipating this work, It would be possible to adjust the morphology of the interstitial electrons by changing the ratio of Li and P and thus obtain compounds with new electronic properties. For example, according to our calculations, the Li 6 P electret is predicted to have a transition temperature superconductor of 39.3 K, breaking the existing registry between the eletrides ".

Predicting the atomic structure of materials from the first principles (based only on their composition) is an extremely challenging task. Typically, it requires the classification of a large number of energy minima into a multidimensional energy surface network. In recent years, researchers have introduced various computational methods that can speed up this process, one of which is called CALYPSO.

"In our study, we used the Calypso program developed by Yanming Ma and his colleagues at Jilin University, which implements a particle swarm optimization algorithm to determine preferred crystal structures, setting the Li: P and pressure relationships as the only initial inputs . "Bergara and Yang explained. "Once we have identified the most stable structures, we have characterized their physical properties, for example, we explore their superconducting properties within the McMillan-Allen-Dynes approximation."

In their study, Bergara, Yang and colleagues reported that a stable Li induced pressure6The electrode P can become a superconductor with a predicted superconducting transition temperature of 39.3K; the highest predicted so far on known electrons. They found that the interstitial electrons of the compound, with states of electrons connected as dumbbells, play a dominant role in this superconducting transition.

"Our prediction not only breaks the superconducting transition temperature record in the electrets, but also allows a better understanding of these materials," said Bergara and Yang.

According to the researchers' predictions, other phosphors rich in Li, such as Li5P, Li11P2Li15P2and Li8P, could also be superconducting electrons, but your TW It is expected to be smaller. This recent study by Bergara, Yang and colleagues may pave the way for further research exploring high-temperature superconductivity in similar binary compounds.

"We believe that research on superconducting electrodes is just beginning," said Bergara and Yang. "As we have shown in this paper, an effective way of designing such superconducting materials is to explore metal electrolyte compounds formed between weak electronegative elements and strong electropositions ".


Explore more:
New method generates higher transition temperature in superconducting materials

More information:
Ziyuan Zhao et al. Predicted Pressure-Induced Superconductor Transition in Eletreto Li6P, Physical Review Letters (2019) DOI: 10.1103 / PhysRevLett.122.097002

Yanchao Wang et al. Prediction of crystal structure through particle-swarm optimization, Physical Review B (2010). DOI: 10.1103 / PhysRevB.82.094116

Journal Reference:
Physical Review Letters

Physical Review B

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