Superconductivity-Induced Ferromagnetism and Weyl Superconductivity in Nb-doped Bi${}_2$Se${}_3$

Abstract

A recent experiment on Nb-doped Bi2Se3 showed that zero field magnetization appears below the superconducting transition temperature. This gives evidence that the superconducting state breaks time-reversal symmetry spontaneously and possibly be in the chiral topological phase. This is in sharp contrast to the Cu-doped case which is possibly in the nematic phase and breaks rotational symmetry spontaneously. By deriving the free energy of the system from a microscopic model, we show that the magnetic moments of the Nb atoms can be polarized by the chiral Cooper pairs and enlarge the phase space of the chiral topological phase compared to the nematic phase. We further show that the chiral topological phase is a Weyl superconducting phase with bulk nodal points which are connected by surface Majorana arcs.

5 pages, 2 figures; 3 pages of Supplementary Material. Comments are welcome

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• Chiral Higgs Mode in Nematic Superconductors
• Andreev Reflection Spectroscopy of Topological Superconductor Candidate Nb${}_x$Bi${}_2$Se${}_3$
• Higher-order Weyl superconductors with anisotropic Weyl-point connectivity
• Weyl points and topological nodal superfluids in a face-centered cubic optical lattice
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• Nematic superconductivity in Cu${}_x$Bi${}_2$Se${}_3$: The surface Andreev bound states
• $\require{mhchem}$Misfit phase $\ce{(BiSe)_{$1.10$}NbSe2}$ as the origin of superconductivity in nobium-doped bismuth selenide
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• Coupled Wire Models of Interacting Dirac Nodal Superconductors
• Resolving different pairing states in Weyl superconductors through the single-particle spectrum
• The absence of Ginzburg-Landau mechanism for vestigial order in the normal phase above a two-component superconductor
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• Pauli paramagnetism of triplet Cooper pairs in a nematic superconductor
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• Weyl superconductivity and quasiperiodic Majorana arcs in quasicrystals
• Possible two-component pairings in electron-doped Bi${}_2$Se${}_3$ based on a tight-binding model
• Anomalous Josephson Hall effect in doped topological insulators with the nematic superconductivity
• Surface chiral superconductivity in odd-parity nematic superconductors with magnetic impurities