Computational Materials Discovery for Lanthanide Hydrides at high pressure: predicting High Temperature superconductivity

Abstract

Hydrogen-rich superhydrides are believed to be very promising high-Tc superconductors, with experimentally observed critical temperatures near room temperature, as shown in recently discovered lanthanide superhydrides at very high pressures, e.g. LaH10 at 170 GPa and CeH9 at 150 GPa. With the motivation of discovering new hydrogen-rich high-Tc superconductors at lowest possible pressure, quantitative theoretical predictions are needed. In these promising compounds, superconductivity is mediated by the highly energetic lattice vibrations associated with hydrogen and their interplay with the electronic structure, requiring fine descriptions of the electronic properties, notoriously challenging for correlated f systems. In this work, we propose a first-principles calculation platform with the inclusion of many-body corrections to evaluate the detailed physical properties of the Ce-H system and to understand the structure, stability and superconductivity of CeH9 at high pressure. We report how the prediction of Tc is affected by the hierarchy of many-body corrections, and obtain a compelling increase of Tc at the highest level of theory, which goes in the direction of experimental observations. Our findings shed a significant light on the search for superhydrides in close similarity with atomic hydrogen within a feasible pressure range. We provide a practical platform to further investigate and understand conventional superconductivity in hydrogen rich superhydrides.

High temperature superconductivity in the lanthanide hydrides at extreme pressures

“…At the same time, this La-H and Ce-H bond length reduction is accompanied by a moderate increase in the H-H distance. This behaviour is opposite to what we have previously found in CeH 9 , where both Ce-H and H-H bonds were longer within DMFT treatment [19].…”

“…The role of f orbitals appears to be very important for the superconducting properties in rare-earth hydrates [19]. That is why in the present paper, in addition to LaH 16 with formally empty La f shell, we study also Cerium hydrate (CeH 16 ) with one f electron in the atomic Ce configuration.…”

“…Within the DFT+DMFT quantum embedding approach, the DFT Kohn-Sham eigenstates are used in the calculation of the DMFT Green function [19,32]. We use atomic projectors to define the Anderson Impurity Model (AIM), which is successively solved within the Hubbard-I approximation.…”

“…We find that LaH 16 and CeH 16 have stable P6/mmm space group crystal structures at pressures up to 250 GPa. Additionally, for the recently discovered Cerium hydride, we predict a comparatively high T c , evaluated using our preestablished hierarchical approach [19].…”