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The superconducting gap structure of FeSe remains a debated issue. Here, Hashimoto et al. report momentum dependence of the gap in single- and multi-domain regions of orthorhombic FeSe crystals, revealing an unusual node lifting of the gap structure in multi-domain regions.

The authors employ zero-field muon spin relaxation to study time-reversal symmetry breaking (TRSB) in FeSe_1−xTe_x. For x = 0.64 with the highest superconducting transition temperature T_c = 14.5 K, which is known to host a topological surface state and Majorana zero modes within vortices, they find a TRSB superconducting state in the bulk.

Low-temperature thermal-transport measurements of a frustrated organic magnet in which a quantum spin-liquid is believed to exist, suggest that the emergence of this state is accompanied by a spin-gap. This contradicts previous studies conducted at higher temperatures, suggesting that our understanding of this system should be re-evaluated.

Light-matter interactions can be used to induce a superconducting-like state in some cuprate superconductors at temperatures above the expected transition temperature. Here, the authors provide time and angle resolved spectroscopic evidence to suggest that photo induced superconductivity can also be achieved in Fe-based superconductors

Uranium ruthenium silicide exhibits a discontinuity in its specific heat at 17.5 K. The underlying cause of this anomaly is hotly debated. A first-principles study of high-order correlations in its electronic structure suggests this behaviour is the result of the emergence of rank-5 nematic order.

Over the years the iron-based superconductors have become a platform to investigate many different phenomena such as the interplay between magnetism and superconductivity, nematicity and topological superconductivity. Here, the authors apply nuclear magnetic resonance to S-substituted FeSe in order to probe spin fluctuations, which indicate the presence of Bogoliubov Fermi surfaces.

The heavy-fermion superconductor UTe₂ likely exhibits spin-triplet Cooper pairing, although a singlet component is possible. Here, using magnetic penetration depth measurements, the authors find evidence consistent with chiral B_3u+iA_u spin-triplet superconductivity in UTe₂.

Previous studies of magnetic Bose–Einstein condensates have been limited to magnetic materials with small spin numbers. Here the authors study the magnetic phase diagram of a S = 3/2 quantum antiferromagnet and show a double dome structure that is attributed to different types of condensates.

Non-Abelian phase of Kitaev quantum spin liquid is promising for topological quantum computation. Here, the authors propose a way to identify the non-abelian Kitaev quantum spin liquid by magnetic field angle dependence, providing criteria for such a state for future experiments.

Kagome metal family, AV3Sb5(A = K, Rb, Cs), provide a platform to probe the interplay between superconductivity (SC) and charge density waves (CDW) and whether it is competitive or complementary. Here, the authors find a contrasting behavior that, while the superconductivity in A = Cs is susceptible to disorder, that in A = K, Rb is stabilized by disorder due to the competitive nature between the CDW and SC states. They attribute the results to the different CDW patterns in A = Cs and A = K, Rb, highlighting crucial role of CDW order to the SC order parameters in the kagome family.

Recent advances in synthetic methods have allowed for the isolation and observation of superconductivity in nickelate compounds, but the exact nature of underlying mechanisms is still to be clarified. Here, the authors investigate the effect of nonmagnetic impurities on the superconductivity of La₃Ni₂O₇ under high-pressure and how this can impact differently on the s and d-wave order parameters.

The BCS-BEC crossover is typically observed using ultracold atomic systems but recent experiments suggest investigations may also be possible using strongly correlated systems. Here, the authors use FeSe_1−xS_x to investigate the evolution of the superconducting state in the BCS-BEC crossover regime observing multiband nature of the BCS-BEC crossover with a suppression of the nematic order upon S-substitution.

The role nematicity and magnetic fluctuations play in the manifestation of unconventional superconductivity for Fe-based superconductors is actively debated with, so far, no clear consensus. Here, the authors study the resistive properties of sulfur-doped FeSe under applied pressure finding evidence of two distinct contributions to the electrical resistivity, which suggest a decoupling of nematic and magnetic fluctuations in this system.

Understanding the effect of the subtle interplay between strong and weak coupling regimes on the properties of quasiparticles is key to understanding unconventional superconductivity. Here, X-ray spectroscopies reveal the partially localized and itinerant magnetic character of quasiparticles in a doped iron pnictide material.