Nathan Prouse | Searcharxiv

arXiv2026

Stacking-dependent anisotropic altermagnetism in V$_{1/3}$NbS$_2$

We report profound impacts of the stacking sequence of triangular lattices of magnetic transition metal ions intercalated between the layers of the van der Waals material NbS$_2$. Using single crystal x-ray and neutron diffraction, and transport and magnetization measurements, we show there are two distinct polytypes of $\rm V_{1/3}NbS_2$ with disparate easy axes of magnetization and different anomalous Hall responses. Self-consistent analysis of inelastic neutron scattering data provides evidence for oscillatory RKKY interactions that extend to 1 nm and stabilize quasi-collinear A-type altermagnetic orders in both polytypes though with perpendicular easy axes. The detailed stacking sequence of a bulk polytype crystal dramatically impact its macroscopic anomalous Hall response and magnetism, which suggests a new path to engineer the bulk properties of a layered three dimensional solid.

cond-mat.str-el↗

arXiv2025

Gliding microtubules exhibit tunable collective rotation driven by chiral active forces

How chirality propagates across scales remains an open question in many biological and synthetic systems. An especially clear manifestation of this propagation is found in in vitro gliding assays of cytoskeletal filaments on surfaces, driven by molecular motors. These assays have become model systems of active matter dynamics, as they spontaneously organize into diverse dynamical states, including collective motions with chiral rotation. However, the microscopic mechanisms underlying these chiral collective dynamics have remained unclear. Here, we investigate rotating active nematic order in microtubule gliding assay experiments under two stabilization conditions, each on two types of substrates. We propose that chirality in active forces exerted by motors on microtubules represents a viable mechanism for this large-scale chirality. Using Brownian dynamics simulations of self-propelled, semiflexible filaments with chiral activity, we demonstrate that coherently rotating active nematic order emerges by this mechanism even in the absence of curvature, i.e. shape chirality, of the constituent filaments. Moreover, we predict that the angular speed and handedness of the collective rotation can be tuned by modulating filament stiffness. Our findings identify a new set of sufficient microscopic ingredients for predictable propagation of chiral handedness from the molecular to the material scale in living and active matter.

cond-mat.soft↗