Daily Overview: Today’s highlighted work focuses on an in-depth understanding of electron correlations, phase fluctuations, and experimental characterization methods in nickel-based superconductors. In [1], RIXS studies on La$_{3-x}$Sr$_x$Ni$_2$O$_7$ thin films reveal that double-stripe spin excitations remain robust within the superconducting dome but collapse sharply in the overdoped non-superconducting regime, directly establishing a link between magnetism and superconductivity. In [2], nano-patterning enhances phase fluctuations in Nd$_{0.8}$Sr$_{0.2}$NiO$_2$, leading to the observation of a two-stage superconducting transition, an anomalous metallic state, and an anisotropy reversal of the in-plane/out-of-plane critical fields, highlighting the potential of phase coherence engineering in strongly correlated systems. In [3], addressing the controversial estimation of the superconducting shielding volume fraction in pressurized Ruddlesden-Popper nickelates, it is clarified that the self-consistent method based on demagnetization factor correction is the standard and correct approach, while the linear assumption of the opposing party leads to an underestimation of the shielding fraction. These works advance the understanding of the mechanism and characterization of nickel-based superconductivity from the perspectives of spin excitations, quantum phase effects, and measurement methodology, respectively. arXiv submission processing window: 2026-03-03 00:00 to 2026-03-03 00:00 UTC.

1. Doping evolution of spin excitations in La$_{3-x}$Sr$_{x}$Ni$_2$O$_7$/SrLaAlO$_4$ superconducting thin films

Summary: Using Ni (L_3)-edge resonant inelastic X-ray scattering (RIXS), this work systematically investigates the evolution of electronic and spin excitations with carrier doping in coherently compressively strained La(_{3-x})Sr(_x)Ni(_2)O(_7)/SrLaAlO(_4) thin films, covering the superconducting ((x = 0, 0.09, 0.21)) and overdoped non-superconducting ((x = 0.38)) regimes. In the superconducting films, dispersive spin excitations persist along the ([H,H]) and ([H,0]) directions, with the dispersion remaining almost doping-independent and exhibiting minimal damping, while the spectral weight only moderately decreases, indicating robust bistripe spin correlations. However, in the non-superconducting film at (x = 0.38), the magnetic response becomes strongly broadened and weakened, accompanied by significantly enhanced damping and a spectral weight reduction of approximately 50%, signaling the collapse of coherent bistripe spin excitations. The simultaneous disappearance of magnetic coherence with superconductivity directly establishes the link between doping-controlled magnetism and superconductivity in layered nickelate thin films.

2. Emergent quantum phenomena via phase-coherence engineering in infinite-layer nickelate superconductors

  • Relevance Score: 4.7657
  • Authors: Haoran Ji, Zheyuan Xie, Xiaofang Fu, Zihan Cui, Minghui Xu, Guang-Ming Zhang, Yi-feng Yang, Haiwen Liu, Yi Liu, Liang Qiao, Jian Wang
  • Affiliations: Tsinghua University, Hefei National Laboratory, University of Chinese Academy of Sciences, Collaborative Innovation Center of Quantum Matter, Songshan Lake Materials Laboratory, Chinese Academy of Sciences, Beijing Normal University, University of Electronic Science and Technology of China, Fudan University, ShanghaiTech University, Renmin University of China, Peking University
  • Link: https://arxiv.org/abs/2603.00670
  • Paper page: Emergent quantum phenomena via phase-coherence engineering in infinite-layer nickelate superconductors

Summary: By fabricating periodic nanohole arrays to construct infinite-layer nickelate superconducting thin films (Nd₀.₈Sr₀.₂NiO₂) into Josephson junction arrays, researchers systematically enhanced the phase fluctuations of the system. In the nanopatterned films, the weakening of macroscopic phase coherence drives the superconducting transition to exhibit a two-stage characteristic and ultimately tends toward an anomalous metallic ground state with saturated resistance. The emergence of charge-2e quantum oscillations indicates inter-array coherence, while the anomalous zero-field magnetoresistance peak marks the persistence of extreme quantum phase fluctuations down to very low temperatures. Notably, through the synergistic enhancement of nanopatterning and magnetic fields, a reversal of superconducting anisotropy is observed in Nd-nickelates, where the in-plane critical field becomes lower than the out-of-plane critical field. The evolution of this anisotropy may reveal an intrinsic exchange Zeeman field coupled to collective electronic states. These results elucidate how superconductivity evolves in response to phase fluctuations and establish nanopatterning as an effective paradigm for unveiling hidden intertwined orders in strongly correlated systems.

3. On estimating superconducting shielding volume fraction from susceptibility in pressurized Ruddlesden-Popper nickelates: Response to arXiv:2602.19282

Summary: This response paper clarifies the evaluation method of the superconducting shielding volume fraction in pressurized Ruddlesden-Popper nickelates. The authors point out that their method directly follows the standard magnetostatic self-consistency relation for finite samples (Equations 2–4), where the measured susceptibility is corrected by the demagnetization factor N to obtain the intrinsic susceptibility, from which the shielding volume fraction is estimated as f ≈ −χ. This method has been widely adopted in the superconductor literature for decades. Taking single-crystal sample S6 as an example, the self-consistent formula yields a superconducting shielding volume fraction of approximately 86% at 50 GPa and 5 K, and about 82% at 40 GPa. The authors argue that the fundamental flaw in the critique presented in arXiv:2602.19282 lies in the assumption by the opposing party that the measured diamagnetic moment is linearly proportional to the superconducting shielding volume fraction, and their simple normalization via calculating the full-shielding Meissner moment. This assumption is invalid for thin disk-shaped samples with strong demagnetization, because the internal field and magnetization are self-consistently coupled through the demagnetizing field, resulting in a nonlinear relationship between the measured moment and the shielding fraction, and consequently yielding an underestimated value of about 60% by the opposing method. The paper also discusses the applicability of the single-demagnetization-factor framework, noting that the sample has a uniform structure and high quality, supporting this macroscopic description, while the artificially constructed phase-separation model by the opposing party is not applicable here. The authors conclude that the method based on magnetostatic self-consistency is correct and a widely adopted standard approach.