Nofar Fridman, Feld, Tomer Daniel, Noah, Avia , Zalic, Ayelet , Markman, Maya , Devidas, T R, Zur, Yishay , Grynszpan, Einav , Gutfreund, Alon , Keren, Itai , Vakahi, Atzmon , Remennik, Sergei , Watanabe, Kenji , Taniguchi, Takashi , Huber, Martin Emile , Aleiner, Igor , Steinberg, Hadar , Agam, Oded , and Anahory, Yonathan . 2025. “Anomalous Thickness Dependence Of The Vortex Pearl Length In Few-Layer Nbse2”. Nature Communications, 16, Pp. 2696. doi:10.1038/s41467-025-57817-3. Publisher's VersionAbstract
The coexistence of multiple types of orders is a common thread in condensed matter physics and unconventional superconductors. The nature of superconducting orders may be unveiled by analyzing local perturbations such as vortices. For thin films, the vortex magnetic profile is characterized by the Pearl-length $Λ$ Λ , which is inversely proportional to the 2D superfluid density; hence, normally, also inversely proportional to the film thickness, $$d$$ d . Here we employ the scanning SQUID-on-tip microscopy to measure $Λ$ Λ in NbSe 2 flakes with thicknesses ranging from $$N=3$$ N = 3 to $$53$$ 53 layers. For $$N\, > \,10$$ N > 10 , we find the expected dependence $$Λ\propto 1/d$$ Λ ∝ 1 / d . However, six-layer films show a sharp increase of $Λ$ Λ deviating by a factor of three from the expected value. This value remains fixed for $$N=3$$ N = 3 to $$6$$ 6 . This unexpected behavior suggests the competition between two orders; one residing only on the first and last layers of the film while the other prevails in all layers.
Contrary to conventional nanoparticle, we report an increasing coercivity of magnetic nanoparticles with decreasing size. Our results show that the anomaly in coercivity can be attributed to a magnetic edge state.
Nano‐patterned magnetic materials have opened new venues for the investigation of strongly correlated phenomena including artificial spin‐ice systems, geometric frustration, and magnetic monopoles, for technologically important applications such as reconfigurable ferromagnetism. With the advent of atomically thin 2D van der Waals (vdW) magnets, a pertinent question is whether such compounds could make their way into this realm where interactions can be tailored so that unconventional states of matter can be assessed. Here, it is shown that square islands of CrGeTe 3 vdW ferromagnets distributed in a grid manifest antiferromagnetic correlations, essential to enable frustration resulting in an artificial spin‐ice. By using a combination of SQUID‐on‐tip microscopy, focused ion beam lithography, and atomistic spin dynamic simulations, it is shown that a square array of CGT island as small as 150 × 150 × 60 nm 3 have tunable dipole–dipole interactions, which can be precisely controlled by their lateral spacing. There is a crossover between non‐interacting islands and significant inter‐island anticorrelation depending on how they are spatially distributed allowing the creation of complex magnetic patterns not observable at the isolated flakes. These findings suggest that the cross‐talk between the nano‐patterned magnets can be explored in the generation of even more complex spin configurations where exotic interactions may be manipulated in an unprecedented way.
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