Evolution of multigap superconductivity in the atomically thin limit: Strain-enhanced three-gap superconductivity in monolayer MgB2

Abstract

Starting from first principles, we show the formation and evolution of superconducting gaps in MgB2 at its ultrathin limit. Atomically thin MgB2 is distinctly different from bulk MgB2 in that surface states become comparable in electronic density to the bulk-like σ-and π-bands. Combining the ab initio electron-phonon coupling with the anisotropic Eliashberg equations, we show that monolayer MgB2 develops three distinct superconducting gaps, on completely separate parts of the Fermi surface due to the emergent surface contribution. These gaps hybridize nontrivially with every extra monolayer added to the film, owing to the opening of additional coupling channels. Furthermore, we reveal that the three-gap superconductivity in monolayer MgB2 is robust over the entire temperature range that stretches up to a considerably high critical temperature of 20 K. The latter can be boosted to >50 K under biaxial tensile strain of ∼ 4%, which is an enhancement stronger than in any other graphene-related superconductor known to date.

The Role of Odd‐Frequency Pairing in Multiband Superconductors

“…Still, we here briefly mention that recent advances, coupling ab initio techniques and Eliashberg theory, have suggested the possibility of realizing odd‐ω superconducting gaps in the multiband superconductor MgB 2 , but only in the presence of a magnetic field . We also note that a growing body of evidence suggests that strong‐coupling effects can play an important role in some of the physics of multiband superconductors …”

Influence of electron–phonon coupling strength on signatures of even and odd-frequency superconductivity

“…Moreover, such a protocol could be applied to other groups of superconducting materials that share similar coupling and retardation properties where experimental conditions for the observation of the paramagnetic Meissner effect could be further optimized. Promising examples could be the recently proposed twodimensional single and few-layer MgB 2 superconductors [11,13,69].…”

Monolayer AsTe2: Stable Robust Metal in 2D, 1D and 0D

“…Since 2H and 1T phases are common structures in 2D TMDs, the both of structures of AsTe 2 monolayer can be used as the non‐gold contact for low‐cost switching device applications. Owing to their non‐magnetic robust metallicity, the investigation electron‐phonon coupling and possible evolution of superconducting characteristics, of AsTe 2 monolayers under confinement can be an attractive topic for future studies.…”