Bosonic Phases Demonstrate 2e Cooper Pairing Across Superconductor-Insulator Transitions

Key Takeaways

• Bosonic excitations observed via h/2e magnetoresistance oscillations
• Nanopatterned etching tunes disorder, driving superconductor‑insulator transition
• Two metallic states: magnetic‑field‑sensitive and zero‑field persistent
• Cooper‑pair fluctuations dominate transport across transition
• Nickelates emerge as platform for bosonic superconductivity research

Pulse Analysis

Infinite‑layer nickelate superconductors have rapidly become a focal point for condensed‑matter research, offering a rare bridge between cuprate physics and emergent quantum phenomena. Their unconventional pairing symmetry and high critical temperatures have spurred intense debate over whether charge carriers behave as fermionic quasiparticles or as bound bosonic entities. By establishing a controllable bosonic landscape through precise nanopatterning, the new study provides a concrete experimental platform to test theoretical models that previously relied on indirect signatures.

The team employed anodized‑aluminum‑oxide masks and reactive‑ion etching to carve a periodic network of superconducting islands within ~9 nm Sm₀.₉₅₋ₓEuₓCa₀.₀₅NiO₂ films. Incremental etching increased disorder, systematically suppressing the superconducting transition while preserving the crystal lattice, as confirmed by X‑ray diffraction. Magnetotransport measurements revealed h/2e oscillations, a hallmark of 2e Cooper‑pair coherence, even as the system entered an insulating regime. Notably, two distinct anomalous metallic phases emerged: one that vanished under modest magnetic fields and another that remained robust at zero field, underscoring the pivotal role of vortex dynamics and bosonic excitations in shaping the ground state.

These observations reshape the narrative around nickelate superconductivity, suggesting that Cooper‑pair fluctuations can dominate charge transport across disorder‑driven transitions. For the broader quantum‑materials community, the work hints at new device concepts that exploit bosonic transport, such as low‑dissipation interconnects or vortex‑based logic elements. Future investigations will likely explore stoichiometric tuning, multi‑layer architectures, and real‑time vortex imaging to unravel the interplay between bosonic and fermionic modes, accelerating the translation of nickelate physics into practical quantum technologies.