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

Abstract

Employing the density-functional theory with local density approximation, we show that the fully hydrogenated monolayer-hexagonal boron nitride (H2BN) has a direct-band gap of 2.96 eV in the blue-light region while the pristine h-BN has a wider indirect-band gap of 4.78 eV. The hole-doped H2BN is stable at low carrier density (n) but becomes dynamically unstable at higher n. We predict that it is a phonon-mediated superconductor with a transition temperature (Tc) which can reach ∼31 K at n of 1.5× 10 14 holes cm −2 near the lattice instability. The Tc could be enhanced up to ∼82 K by applying a biaxial tensile strain at 6 % along with doping at n of 3.4× 10 14 holes cm −2 close to a new lattice instability.

Superconducting dome in ferroelectric-type materials from soft mode instability

“…The role of structural instability, and its influence on superconductivity, similar to what happens in ferroelectrics 20 , is also a highly debated topic in the context of high-temperature superconductors, both cuprates 21,22 and the recently discovered hydrides under high pressure [23][24][25] , and, in general, in strongly coupled superconductors 26 . For example, it is well known that, before the discovery of cuprates, high-T c superconductivity was sought in A15 intermetallic compounds which exhibit soft-mode structural instability 27 .…”