Daily Overview: Today’s highlight focuses on the multi-dimensional advancement of pairing symmetry, thin-film property control, and high-pressure spectroscopic characterization in nickelate superconductors. Theoretical studies reveal that in pressurized La₃Ni₂O₇, correlation-driven self-energy renormalization fundamentally reshapes the pairing hierarchy: upon incorporating the dynamical mean-field self-energy, the dominant pairing symmetry reverses from the B₂g dxy state given by conventional RPA to an A₁g s± state, indicating that correctly accounting for the correlation renormalization of quasiparticles is essential for predicting the pairing symmetry of bilayer nickelates. On the experimental side, Nd₁₋ₓEuₓNiO₂ infinite-layer films grown by pulsed laser deposition exhibit a broad superconducting dome in the range 0.2 ≤ x ≤ 0.5, with an optimal superconducting transition temperature as high as about 31 K at x = 0.3, outperforming results from other vacuum epitaxy techniques, and both underdoped and overdoped regions display magnetic-field-enhanced and reentrant superconductivity induced by the polarization of Eu²⁺ local magnetic moments. Furthermore, a newly developed high-pressure soft point-contact Andreev reflection spectroscopy technique has detected, for the first time in the bilayer nickelate La₂PrNi₂O₇, a sharp zero-bias conductance peak whose evolution with temperature, magnetic field, and pressure is characteristic of unconventional superconductivity and possible d-wave pairing symmetry, thus providing direct evidence from the microscopic spectroscopic perspective for elucidating the pairing mechanism in nickelate superconductors. arXiv submission processing window: 2026-07-14 00:00 to 2026-07-14 00:00 UTC.

1. Correlation-renormalized spin-fluctuation pairing and the stabilization of $s_{\pm}$ superconductivity in pressurized La$_3$Ni$_2$O$_7$

Summary: To resolve the unsettled superconducting pairing symmetry in pressurized La₃Ni₂O₇, this study employs a four-orbital Wannier Hamiltonian and incorporates the self-energy from single-site two-orbital dynamical mean-field theory (DMFT) into the random phase approximation (RPA), constructing self-energy-renormalized particle–hole bubbles to replace the bare bubbles while retaining the same local Slater-Kanamori interaction vertices. Conventional RPA calculations reveal that the dominant pairing belongs to the B₂g dxy channel, but once the DMFT self-energy is included, the pairing hierarchy is reversed: the sign-changing A₁g s± state becomes dominant, the B₁g dx²-y² channel takes the second place, and the original B₂g instability is strongly suppressed. Pocket-resolved decomposition and orbital-resolved susceptibility analyses show that this reversal originates from the selective renormalization of the d3z²-r² orbital, which filters out γ-pocket scattering processes that favor dxy pairing while preserving distributed inter-pocket scattering conducive to s±. Further employing the dual Bethe-Salpeter equation with local DMFT vertices to compute the static spin susceptibility yields a broad finite-momentum magnetic response that is weak near the Γ point, reinforcing the spin-fluctuation background for the s± state at the two-particle level. These results demonstrate that strong correlation effects in La₃Ni₂O₇ are not minor corrections; properly treating correlation-renormalized quasiparticles is essential for accurately predicting the superconducting pairing symmetry.

2. Superconducting dome and field-enhanced superconductivity of PLD synthesized Nd1-xEuxNiO2 thin films

Summary: Researchers successfully synthesized a series of infinite-layer Nd₁₋ₓEuₓNiO₂ thin films with doping extended to x = 0–0.7 using pulsed laser deposition combined with calcium hydride topotactic reduction. Electrical transport measurements reveal a superconducting dome in the range 0.2 ≤ x ≤ 0.5, whose doping width is larger than that of samples fabricated by molecular beam epitaxy and comparable to that achieved by chemical solution methods. The film with x = 0.3 exhibits an optimal superconducting transition temperature of about 31 K, significantly higher than values obtained by other vacuum epitaxy techniques, indicating that pulsed laser deposition is an effective route for preparing high-quality, high-transition-temperature nickelate superconducting thin films. Magnetotransport experiments observe robust magnetic-field-enhanced and re-entrant superconductivity in both underdoped and overdoped regions, attributed to the polarization of Eu²⁺ local magnetic moments under an external field that generates an internal exchange field partially compensating the applied field; the Jaccarino-Peter effect alone cannot fully explain this phenomenon, suggesting the existence of additional mechanisms. In the low-temperature region just above the onset superconducting transition temperature, the Hall resistance exhibits a nonlinear character without noticeable magnetic hysteresis, which may arise from magnetic impurity scattering. These results highlight the critical role of magnetic rare-earth Eu²⁺ ions in imparting exotic physical properties to infinite-layer nickelates.

3. Soft point-contact Andreev reflection spectroscopy in a palm-type cubic anvil-pressure cell

Summary: Researchers integrated soft point-contact Andreev reflection spectroscopy into a palm-type cubic anvil high-pressure cell, employing substrate anchoring and an external wire branching strategy to stably form multiple point-contact junctions under hydrostatic pressures up to 15 GPa. Benchmark measurements on the elemental superconductor Nb verified the method’s reliability and yielded a zero-temperature superconducting energy gap ratio of 2Δ(0)/k_B T_c ≈ 3.3. Further application to the kagome metal superconductor CsCr3Sb5 and the bilayer nickelate superconductor La2PrNi2O7 revealed sharp zero-bias conductance peaks strikingly different from those of conventional BCS superconductors, and their evolution with temperature, magnetic field, and pressure was systematically investigated. Analysis indicates that these spectroscopic features are consistent with unconventional superconductivity and possible d-wave pairing symmetry, providing direct spectroscopic evidence for understanding their pairing mechanism. This work successfully establishes a high-pressure experimental platform that bridges macroscopic electrical transport and microscopic spectroscopic probes, opening a new avenue for broadly exploring the pairing symmetries of pressure-induced unconventional superconductors.