Scandium's electrons may explain predicted room-temperature superconductivity

Good news!

"Scientists have confirmed the existence of a predicted room temperature superconductor, while explaining the microscopic mechanism that distinguishes it from a similar one discovered several years ago. The work, published in the journal Physical Review B, offers "a theoretical blueprint for the future design of superior superconductor hydrides" ...

These metal clathrate superhydrides have unit cells—the smallest repeatable unit—made up of metallic elements surrounded by a "cage" of hydrogen ions. (The structure of LaSc2H24 has fully enclosed lanthanum in a cage of 30 hydrogen atoms and partially enclosed scandium atoms in cages of 24 hydrogen ions.)

Hydrogen atoms occupy three inequivalent sites forming these anisotropic layers, creating structurally different properties between the two different layers. The material's anisotropy opens two different superconductivity channels, each having a different value for the critical temperature. ..."

From the abstract:

"The discovery of LaSc2⁢H24 represents an advance in the quest for room-temperature superconductivity, yet the microscopic mechanism underlying its high-temperature superconductivity remains unclear.

Through a comprehensive revisit of theoretical analysis, we uncover a pivotal transition from the anisotropic two-gap superconductivity of LaH10 to an isotropic single-gap superconductivity in LaSc2⁢H24 upon the introduction of scandium, thereby enhancing the superconducting critical temperature (𝑇c).

This enhancement is rooted in a critical dual role of Sc 3⁢𝑑 electrons:
(i) the Sc-derived Jahn-Teller effect promotes hydrogen metallization via the elongation of specific interlayer H-H bonds and enhances electron-phonon coupling (EPC) through the softening of associated phonon modes;
(ii) Sc 3⁢𝑑 electrons reconstruct the electronic structure into an MgB2-like configuration, generating Sc-H-Sc 𝜎- and 𝛿-bonding states with EPC strengths comparable to LaH10.

Crucially, the pronounced orbital overlap between Sc and the hydrogen cages effectively unifies these two contributions on the Fermi surface. This Sc-induced gap unification bridges the high-EPC H-H states with widespread Sc-H states, establishing an isotropic single-gap nature with a large overall EPC strength.

Our findings identify this Sc-induced gap unification as the fundamental mechanism for achieving room-temperature superconductivity in LaSc2⁢H24, offering a theoretical blueprint for the future design of superior superconducting hydrides."

Scandium's electrons may explain predicted room-temperature superconductivity

Isotropic superconductivity in the room-temperature superconductor LaSc2⁢H24 (no public access)

Isotropic Superconductivity in Room-temperature Superconductor LaSc (preprint, open access)