Study investigates pressure-induced superconducting transition in electrides | 3/20/2019 | Staff
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The image on the left shows the atomic structure of the Li6P compound, and on the right the electronic charge density is plotted, where the electronic localization at the interstitials can be seen in red. Credit: Zhao et al.

Researchers at Northeast Normal University, in China, and University of the Basque Country, in Spain, have recently carried out a study investigating the superconducting transition of electrides. The researchers observed that a pressure-induced stable Li6P, identified by first-principles swarm structure calculations, can become a superconductor with a considerably high superconducting transition temperature.

Applications - Materials - Understanding - Superconductors - Challenge

"Considering the wide potential applications of superconducting materials, the understanding of high-temperature superconductors is a key scientific challenge in condensed matter physics," Aitor Bergara and Guochun Yang, two of the researchers who carried out the study, told, via email.

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

Electrides - Superconductors - Example - Transition - Temperature

Overall, electrides are very poor superconductors. For example, the experimentally observed superconducting transition temperature of a canonical electride [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 electrides.

"Interestingly, pressure-induced lithium (Li) electride is metallic," Bergara and Yang said. "Additionally, phosphorus (P) presents a moderate electronegativity, so that they can trap some electrons in Li-rich Li-P compounds, while the remaining electrons may remain at interstitial regions. Thus, as we are predicting is this work, it would be possible to adjust the morphology of interstitial electrons by changing the ratio of Li and P and, therefore, obtain compounds with novel...
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