Novel Strongly Correlated Europium Superhydrides

• Published in: arXiv.org 2020-12
• Main Authors: Semenok, Dmitrii V, Zhou, Di, Kvashnin, Alexander G, Huang, Xiaoli, Galasso, Michele, Kruglov, Ivan A, Ivanova, Anna G, Gavrilyuk, Alexander G, Chen, Wuhao, Tkachenko, Nikolay V, Boldyrev, Alexander I, Troyan, Ivan, Oganov, Artem R, Cui, Tian
• Format: Article
• Language: English
• Subjects: Anharmonicity; Antiferromagnetism; Atomic radius; Broken symmetry; Clathrates; Crystal structure; Electron phonon interactions; Equations of state; Europium; Ferromagnetism; Superconductivity
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2012.05595

We conducted a joint experimental-theoretical investigation of the high-pressure chemistry of europium polyhydrides at pressures of 86-130 GPa. We discovered several novel magnetic Eu superhydrides stabilized by anharmonic effects: cubic \(EuH_{9}\), hexagonal \(EuH_{9}\), and an unexpected cubic (Pm-3n) clathrate phase, \(Eu_{8}H_{46}\). Monte Carlo simulations indicate that cubic \(EuH_{9}\) has antiferromagnetic ordering with T(Neel) up to 24 K, whereas hexagonal \(EuH_{9}\) and Pm-3n-\(Eu_{8}H_{46}\) possess ferromagnetic ordering with T(Curie) = 137 and 336 K, respectively. The electron-phonon interaction is weak in all studied europium hydrides, and their magnetic ordering excludes s-wave superconductivity, except, perhaps, for distorted pseudohexagonal \(EuH_{9}\). The equations of state predicted within the DFT+U approach (the Hubbard corrections were found within linear response theory) are in close agreement with the experimental data. This work shows the great influence of the atomic radius on symmetry-breaking distortions of the crystal structures of superhydrides and on their thermodynamic stability.