Dirac surface states, multiorbital dimerization and superconductivity in Nb- and Ta-based A15 compounds

Abstract

Using first-principle calculations, we investigate the electronic, topological and superconducting properties of Nb${}_3$X (X = Ge, Sn, Sb) and Ta${}_3$Y (Y = As, Sb, Bi) A15 compounds. We demonstrate that these compounds host Dirac surface states which are related to a nontrivial Z${}_2$ topological value. The spin-orbit coupling (SOC) splits the eightfold degenerate R point close to the Fermi level enhancing the amplitude of the spin Hall conductance. Indeed, despite the moderate spin-orbit of the Nb-compounds, a large spin Hall effect is also obtained in Nb${}_3$Ge and Nb${}_3$Sn compounds. We show that the Coulomb interaction opens the gap at the R point thus making more evident the occurrence of Dirac surface states. We then investigate the superconducting properties by determining the strength of the electron-phonon BCS coupling. The evolution of the critical temperature is tracked down to the 2D limit indicating a reduction of the transition temperature which mainly arises from the suppression of the density of states at the Fermi level. Finally, we propose a minimal tight-binding model based on three coupled Su-Schrieffer-Heeger chains with t${}_{2g}$ Ta- and Nb-orbitals reproducing the spin-orbit splittings at the R point among the $\pi$-bond bands in this class of compounds. We separate the kinetic parameters in $\pi$ and $\delta$-bonds, in intradimer and interdimer hoppings and discuss their relevance for the topological electronic structure. We point out that Nb${}_3$Ge might represent a Z${}_2$ topological metal with the highest superconducting temperature ever recorded.

16 pages, 12 figures in main text, 3 figures in appendix, Paper submitted to Physical Review B

References in corpus (40)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• Restoring the density-gradient expansion for exchange in solids and surfaces
• Generalized gradient approximation for solids and their surfaces
• Phonons and related properties of extended systems from density-functional perturbation theory
• Superconducting proximity effect and Majorana fermions at the surface of a topological insulator
• Topological Insulators with Inversion Symmetry
• WannierTools: An open-source software package for novel topological materials
• Search for Majorana fermions in superconductors
• Beyond Dirac and Weyl fermions: Unconventional quasiparticles in conventional crystals
• CsV${}_3$Sb${}_5$: a ${\mathbb{Z}}_2$ topological kagome metal with a superconducting ground state
• Intrinsic spin Hall effect in platinum metal
• Double Dirac Semimetals in Three Dimensions
• Dirac and Weyl Superconductors in Three Dimensions
• Thermodynamic evidence for nematic superconductivity in Cu${}_x$Bi${}_2$Se${}_3$
• Multiple topological states in iron-based superconductors
• Calculation of intrinsic spin Hall conductivity by Wannier interpolation
• A review and prospects for Nb3Sn superconductor development
• Superconductivity in the A15 Structure
• Giant Intrinsic Spin Hall Effect in W${}_3$Ta and other A15 Superconductors
• A comprehensive review on topological superconducting materials and interfaces
• Local invariants identify topology in metals and gapless systems
• Charge density wave instability and pressure-induced superconductivity in bulk 1T-NbS2
• Topological states in A15 superconductors
• Strain sensitivity and superconducting properties of Nb3Sn from first principles calculations
• Revealing Topology in Metals using Experimental Protocols Inspired by $K$-Theory
• Strain-induced stripe phase in charge ordered single layer NbSe${}_2$
• Multiple band-crossings and Fermi surface topology: role of double nonsymmorphic symmetries in MnP-type crystal structures
• Electronic properties of TaAs2 topological semimetal investigated by transport and ARPES
• Correlation-corrected band topology and topological surface states in iron-based superconductors
• Novel ${\mathbb{Z}}_2$-topological metals and semimetals
• Superconductivity in Nb2Pd3Te5 and Chemically-Doped Ta2Pd3Te5
• Stacking effect and Coulomb correlation in layered charge density wave phase of 1T-NbS2
• Pressure-induced nontrivial $Z_2$ band topology and superconductivity in transition metal chalcogenide ${\mathrm{Ta}}_2{\mathrm{Ni}}_3{\mathrm{Te}}_5$
• Topological Superconductivity in Multifold Fermion Metals
• Effects of fabrication routes and material parameters on the control of superconducting currents by gate voltage
• Superconducting properties and gap structure of the topological superconductor candidate Ti_(3)Sb
• Superconducting properties of the spin Hall candidate Ta3Sb with eightfold degeneracy
• Topology of chalcogen chains
• Bismuth antiphase domain wall: A three-dimensional manifestation of the Su-Schrieffer-Heeger model
• ZrOsSi: A $Z_2$ topological metal with a superconducting ground state

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