Ab initio study of orbital-selective superconductivity in $\gamma$-BiPd

Abstract

We investigate the superconducting (SC) properties of experimentally realised $\gamma$-BiPd by solving the anisotropic Migdal-Eliashberg equations in conjunction with {\it ab initio} relativistic calculations of the electron and phonon band structures as well as electron-phonon coupling (EPC) matrix elements. Our study reveals that $\gamma$-BiPd possesses a complex Fermi surface (FS), consisting of two electron pockets and one hole pocket, each characterised by distinct atomic orbitals. Our key finding is that the superconductivity in $\gamma$-BiPd is primarily orbital-selective, arising from Bi $p$-orbitals, and distributed anisotropically on the FS, although contribution from Pd $d$-orbitals, particularly on the hole pocket, is also discernable. While our results show an anisotropic nature of the {\bf k}-dependent SC gap ${\Delta }_{\mathbf{k}}$ and EPC strength ${\lambda }_{\mathbf{k}}$ across the FS, calculated superconducting quasiparticle density of states $N_S$ spectra exhibit a U-shaped gap and ${\Delta }_{\mathbf{k}}$ distribution forms a single peak, being consistent with the spin-singlet $s$-wave superconductivity observed in this material. The calculated $T_c$ is $\sim$2.0 K, agreeing in order of magnitude with the experimental value of 3.3 K in $\gamma$-BiPd thin films. The predicted EPC-enhanced Sommerfeld coefficient ${\gamma }_n$ of $0.141$ mJ/K${}^2$cm${}^3$ is similar to the experimental ${\gamma }_n$ value ($0.119$ mJ/K${}^2$cm${}^3$) of the isoelectronic and isostructural Bi(Pd${}_{0.5}$Pt${}_{0.5}$) alloy.

References in corpus (14)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• Advanced capabilities for materials modelling with Quantum ESPRESSO
• Unconventional pairing originating from disconnected Fermi surfaces in superconducting LaFeAsO${}_{1-x}$F${}_x$}
• Scanning tunneling spectroscopy of high-temperature superconductors
• Superconducting density of states and vortex cores of 2H-NbS2
• Origin of superconductivity and latent charge density wave in NbS${}_2$
• Even Parity, Orbital Singlet and Spin Triplet Pairing for Superconducting $La(O_{1-x}{F}_x)FeAs$
• Dirac Surface States and Nature of Superconductivity in Noncentrosymmetric BiPd
• Two-band superconductors: Hidden criticality deep in the superconducting state
• Room Temperature Superconductivity: the Roles of Theory and Materials Design
• Superconductivity at 5.4 K in $\beta$-Bi${}_2$Pd
• Orbital-selective Band Hybridisation at the Charge Density Wave Transition in Monolayer TiTe${}_2$
• Two-gap superconductivity and decisive role of rare-earth $d$ electrons in infinite-layer nickelates
• Unusual Dirac fermions on the surface of noncentrosymmetric $\alpha$ - BiPd superconductor