High-Temperature Superconductivity in the Lanthanide Hydrides at Extreme Pressures

Yao Wei,Cedric Weber,Terence Tse,Evgeny Plekhanov,Francesco Macheda,Zelong Zhao,Nicola Bonini

doi:10.3390/app12020874

Abstract

Hydrogen-rich superhydrides are promising high-Tc superconductors, with superconductivity experimentally observed 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. Superconductivity is believed to be closely related to the high vibrational modes of the bound hydrogen ions. Here, we studied the limit of extreme pressures (above 200 GPa) where lanthanide hydrides with large hydrogen content have been reported. We focused on LaH16 and CeH16, two prototype candidates for achieving a large electronic contribution from hydrogen in the electron–phonon coupling. 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 and La–H systems and to understand the structure, stability, and superconductivity of these systems at ultra-high pressure. We provide a practical approach to further investigate conventional superconductivity in hydrogen-rich superhydrides. We report that density functional theory provides accurate structure and phonon frequencies, but many-body corrections lead to an increase of the critical temperature, which is associated with the spectral weight transfer of the f-states.

Highlights

We show that the many-body corrections in f orbital systems could cause significant changes, with spectral weight shifts in the order of one electron volt
A change in the spectral weight of the f states caused a rise in the predicted superconducting temperature, which influenced the spectral character at the Fermi level
We obtained a theoretical estimate for LaH16 as Tc = 166.2 K by DFT and Tc = 192.4 K by dynamical meanfield theory (DMFT), as well as a theoretical estimate for CeH16 as Tc = 69.7 K by DFT and Tc = 150.6 K by DMFT, and we discussed the capabilities for relaxing lanthanide hydrides within the DMFT formalism, built on our recent developments providing DMFT forces for underlying ultra-soft and norm-conserving pseudopotentials, despite the fact that many-body corrections have so far been limited to the electronic contributions to the Eliashberg function

Summary

Introduction

In the research of condensed matter [1], pressure is a fundamental thermodynamic variable that determines the state of matter and plays an important role in the field. Hydrogen-rich materials have garnered much attention in regard to obtaining superconductivity at high temperatures and have led to much theoretical and experimental work on the search for the high-temperature superconductivity of hydrides under high pressure [3]. The chemical pre-compression method, proposed by Neil Ashcroft in 2004, has led to the key realisation that hydrogen-rich compounds are a new potential class of high-temperature superconductors [4]. As investigating the high-temperature superconductivity of metallic hydrogen is highly challenging [5], most scholars have instead redirected focus to the synthesis and properties of hydride-rich compounds instead. The realisation of very-high-temperature superconductivity, near room temperature, was discovered in hydrogen disulphide [6,7] and lanthanum hydrogen [8–10], an important set of milestones

Methods

Discussion

Conclusion