Anisotropic Migdal–Eliashberg characterization of multigap superconductivity in YSi2/Si superlattices

Determine whether the in-plane strain and YSi2/Si interfaces in YSi2(0001)/Si(111) superlattices transform the single-gap superconductivity of bulk YSi2 into multigap superconductivity by solving the anisotropic Migdal–Eliashberg equation.

Background

The paper reports that unstrained bulk YSi2 exhibits a single superconducting energy gap despite having multiple electronic bands. It further finds that applying in-plane compressive strain makes multigap features discernible in the calculated superconducting response and argues that YSi2/Si interfaces may have a similar effect.

For the YSi2(0001)/Si(111) superlattices, the authors state that the possible emergence of multigap superconductivity could be tested by solving the anisotropic Migdal–Eliashberg equation. This calculation remains unresolved in the paper because the computation is described as extremely demanding; the reported superlattice transition temperatures are obtained only with the McMillan–Allen–Dynes formula and isotropic Migdal–Eliashberg theory.

References

Theoretically, this could be tested by solving the anisotropic ME equation. This is a very interesting and challenging question that should be delt with seriously in the next steps as the computation is extremely demanding.

— Superconducting $T_\mathrm{c}$ up to 20.6 K in bulk YSi$_2$ and YSi$_2$/Si superlattices due to chemical flattening  (2608.16062 - Li et al., 17 Aug 2026) in Section 2, subsection “Electronic structure, electron-phonon coupling and superconductivity,” final paragraph before Section 3 “Summary”