Prediction of superconductivity and topological aspects in single-layer <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>β</mml:mi><mml:mo>−</mml:mo><mml:msub><mml:mi>Bi</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi>Pd</mml:mi></mml:mrow></mml:math>
Pengfei Liu, Jingyu Li, Xin-Hai Tu, Huabing Yin, Baisheng Sa, Junrong Zhang, David J. Singh, Bao‐Tian Wang
Abstract
Topological superconductors, characterized by topologically nontrivial states residing in a superconducting gap, are a recently discovered class of materials having Majorana fermions. The interplay of superconductivity and topological states gives rise to opportunities for achieving such topological superconductors in condensed matter systems. Up to now, several single-material topological superconductors in this form have been theoretically predicted and experimentally confirmed. Here, using the first-principles calculations, we study the superconducting single-layer $\ensuremath{\beta}\ensuremath{-}{\mathrm{Bi}}_{2}\mathrm{Pd}$. The electronic density of states near Fermi level of this monolayer are dominated by the Bi-$p$ and Pd-$d$ orbitals, forming a two-band Fermi surface with multiclass sheets. The presence of soft phonon bands, in cooperation with the electron susceptibility, accounts for electron-phonon superconductivity of single-layer $\ensuremath{\beta}\ensuremath{-}{\mathrm{Bi}}_{2}\mathrm{Pd}$. With the centrosymmetric structure, single-layer $\ensuremath{\beta}\ensuremath{-}{\mathrm{Bi}}_{2}\mathrm{Pd}$ possesses a continuous gap over the whole Brillouin zone and topological Dirac-like states at its one-dimensional boundary. The present findings would lead to the expectation of one-dimensional topological superconductivity and Majorana bound states in a monolayer candidate of $\ensuremath{\beta}\ensuremath{-}{\mathrm{Bi}}_{2}\mathrm{Pd}$ with intrinsic full-gap superconductivity.