Multiband Nature of the Room-Temperature Superconductivity in Compressed LaH$_{10}$

TL;DR

This paper uncovers the multiband superconducting gaps in compressed LaH$_{10}$, explaining how hybridized electronic states contribute to its high transition temperature, and compares it with YH$_{10}$ to highlight the role of multiple Fermi surface sheets.

Contribution

It reveals the presence of two distinct nodeless, anisotropic superconducting gaps in LaH$_{10}$ and links multiband pairing to high-temperature superconductivity in compressed hydrides.

Findings

Two nodeless, anisotropic superconducting gaps identified.

Large gap mainly from hybridized H s/p orbitals, small gap from H s and La f orbitals.

Enhanced EPC and higher T_c in YH$_{10}$ due to additional Fermi surface sheets.

Abstract

Recently, the discovery of room-temperature superconductivity (SC) was experimentally realized in the fcc phase of LaH$_{10}$ under megabar pressures. This SC of compressed LaH$_{10}$ has been explained in terms of strong electron-phonon coupling (EPC), but the mechanism of how the large EPC constant and high superconducting transition temperature $T_{\rm c}$ are attained has not yet been clearly identified. Based on the density-functional theory and the Migdal-Eliashberg formalism, we reveal the presence of two nodeless, anisotropic superconducting gaps on the Fermi surface (FS). Here, the small gap is mostly associated with the hybridized states of H $s$ and La $f$ orbitals on the three outer FS sheets, while the large gap arises mainly from the hybridized state of neighboring H $s$ or $p$ orbitals on the one inner FS sheet. Further, we find that the EPC constant of compressed YH$_{10}$ with the same sodalite-like clathrate structure is enhanced due to the two additional FS sheets, leading to a higher $T_{\rm c}$ than LaH$_{10}$. It is thus demonstrated that the multiband pairing of hybridized electronic states is responsible for the large EPC constant and room-temperature SC in compressed hydrides LaH$_{10}$ and YH$_{10}$.