Nonadiabatic superconductivity in a Li-intercalated hexagonal boron nitride bilayer

Abstract

When considering a Li-intercalated hexagonal boron nitride bilayer (Li-hBN), the vertex corrections of electron–phonon interaction cannot be omitted. This is evidenced by the very high value of the ratio λωD/εF ≈ 0.46, where λ is the electron–phonon coupling constant, ωD is the Debye frequency, and εF represents the Fermi energy. Due to nonadiabatic effects, the phonon–induced superconducting state in Li-hBN is characterized by much lower values of the critical temperature (T LOVC C ∈ {19.1, 15.5, 11.8} K, for μ* ∈ {0.1, 0.14, 0.2}, respectively) than would result from calculations not taking this effect into account (T ME C∈ {31.9, 26.9, 21} K). From the technological point of view, the low value of T C limits the possible applications of Li-hBN. The calculations were carried out under the classic Migdal–Eliashberg formalism (ME) and the Eliashberg theory with lowest-order vertex corrections (LOVC). We show that the vertex corrections of higher order (λ3) lower the value of T LOVC C by a few percent.

Carbonaceous sulfur hydride system: the strong-coupled room-temperature superconductor with a low value of Ginzburg-Landau parameter

“…( 10) and Eq. ( 11) were used to study of superconducting state in low-dimensional systems such as LiC 6 [53][54][55][56] and Li-hBN [57,58]. In this cases, the dimensionless ratio λω D /ε F reaches high values of 0.09 for LiC 6 and 0.46 for Li-hBN.…”

Phonon-Mediated Superconductivity near the Lattice Instability in Hole-doped Hydrogenated Monolayer Hexagonal Boron Nitride

“…By means of chemical doping of Ca, Ba, and Sr atoms, one may theoretically obtain the superconductivity in monolayer h-BN with T c ranging from ∼1 K to 10 K [22]. The bilayer h-BN with an intercalated Li atom has also been predicted to show the superconductivity with different T c (< 25 K) [23,24]. Despite some efforts being devoted to developing the fundamen-tal understanding of phonon-mediated superconductivity in doped h-BN, the electronic structure, lattice stability, and superconductivity in H 2 BN (fully hydrogenated monolayer h-BN) have not been studied.…”