Superconductivity in CaH and ThH through fully ab initio Eliashberg method and self-consistent Green's function.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Mechanics

Background:

• Pressurized hydrogen-based compounds are promising phonon-mediated superconductors.
• The electronic density of states (DOS) near the Fermi energy significantly impacts superconducting transition temperature (Tc).
• Previous studies highlighted peak structures in DOS for materials like H3S and LaH.

Purpose of the Study:

• To investigate the influence of a dip structure in the DOS on superconductivity in CaH and ThH.
• To compare the behavior of materials with DOS dips versus those with DOS peaks.
• To unify the understanding of how DOS structures affect Tc calculations.

Main Methods:

• Utilized the fully ab initio Eliashberg theory.
• Employed a self-consistent treatment of the electron Green's function.
• Calculated superconducting transition temperatures for CaH and ThH under high pressure.

Main Results:

• Calculated Tc for CaH (225-235 K at 200 GPa) and ThH (156-158 K at 170 GPa) align with experimental data.
• Demonstrated that a dip structure in the DOS leads to different Tc behavior compared to peak structures.
• Provided quantitative agreement with experimental findings for CaH and ThH.

Conclusions:

• The energy dependence of the DOS around the Fermi level is crucial for evaluating Tc in these materials.
• This work reconciles the understanding of how both peak and dip structures in DOS influence Tc.
• The findings offer a unified perspective on DOS effects in high-pressure superconductors.