Time-reversal symmetry-breaking nematic superconductivity in FeSe

Abstract

FeSe is a unique member of the family of iron-based superconductors, not only because of the high values of $T_c$ in FeSe monolayer, but also because in bulk FeSe superconductivity emerges inside a nematic phase without competing with long-range magnetic order. Near $T_c$, superconducting order necessarily has $s+d$ symmetry, because nematic order couples linearly the $s$-wave and $d$-wave harmonics of the superconducting order parameter. Here we argue that the near-degeneracy between $s$-wave and $d$-wave pairing instabilities in FeSe, combined with the sign-change of the nematic order parameter between hole and electron pockets, allows the superconducting order to break time-reversal symmetry at a temperature $T^{\ast }<T_c$. The transition from an $s+d$ state to an $s+{\mathrm{e}}^{i\alpha }d$ state should give rise to a peak in the specific heat and to the emergence of a soft collective mode that can be potentially detected by Raman spectroscopy.

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Cited by in corpus (13)

• Exotic Superconducting States in FeSe-based Materials
• Two superconducting states with broken time-reversal symmetry in FeSe1-xSx
• Non-local $d_{xy}$ nematicity and the missing electron pocket in FeSe
• Pairing symmetry and topological surface state in iron-chalcogenide superconductors
• FeSe and the missing electron pocket problem
• High-order Time-Reversal Symmetry Breaking Normal State
• Interplay between nematicity and Bardasis-Schrieffer modes in the short-time dynamics of unconventional superconductors
• Spontaneous magnetization in unitary superconductors with time reversal symmetry breaking
• Atomic-scale Frustrated Josephson Coupling and Multi-condensate Visualization in FeSe
• Atomic scale imaging of sign-changing order parameter in superconducting FeSe with Tunneling Andreev Reflection
• On the existence of nematic-superconducting states in the Ginzburg-Landau regime
• Superconductivity near an Ising nematic quantum critical point in two dimensions
• Specific Heat and the gap structure of a Nematic Superconductor, application to FeSe