How a Nickel Impurity Turns a Superconductor into a Magnetic Tangle ⚡ экспресс
Single crystals of Ni₀.₁₉NbSe₂ exhibit antiferromagnetic order below 23.5 K with magnetic frustration (irreversibility at ~10 K, hysteresis) and Curie-Weiss anisotropy: –80 K (in-plane) and –137 K (out-of-plane), indicating spin alignment along the c-axis. Charge density waves and superconductivity are fully suppressed down to 300 mK. ARPES at 84 K reveals an electron pocket at Γ̅ and a shift of the Van Hove singularity — the reason for the disappearance of the orderings. These data confirm predictions about the stabilization of frustrated stripe structures and Fermi surface reconstruction due to cationic disorder upon nickel intercalation. Ni₀.₁₉NbSe₂ is in a magnetically frustrated non-superconducting regime, illustrating the key role of partial intercalation and disorder in low-dimensional quantum materials.
Niobium diselenide is a layered material that conducts current without resistance at low temperatures. If you weave nickel atoms between its layers, like extra threads in a fabric, superconductivity vanishes. In its place, a tangled magnetic disorder appears: the nickel "magnetic arrows" can't align into a simple pattern because each neighbor demands the opposite direction. The result is a magnetic tangle — frustrated and inhomogeneous. When cooled below –250 °C, it freezes, but there's no long-range order, and its behavior depends on the direction within the layers.
Using photoemission spectroscopy, the reason was uncovered: a key point where electrons cluster shifted, suppressing superconductivity. An unexpected twist: cool it just ten degrees colder, and this tangle shows magnetic memory — it "remembers" the previous magnetization, like a frozen knot you don't want to untie. A tiny addition completely reshapes the properties, opening a path to creating materials with tailored characteristics.
🎯 Pure niobium diselenide is one of the few materials where superconductivity and periodic electron clusters coexist. Adding nickel erases both, creating magnetic disorder with its own memory.