arXiv subjects

Luca Maranzana

Publications and source records attributed to Luca Maranzana.

4 recordsLinked to original sources

arXiv2026

Phase-Space Quantum Geometry Beyond Adiabatic Electron Dynamics

The geometry of electronic quantum states plays an important role in the equilibrium and transport properties of solids. While the Berry curvature is known to influence electron motion, recent work has shown that the quantum metric also affects the motion of electron wave packets beyond the adiabatic approximation. To connect this nonadiabatic dynamics to many-electron observables, we derive an equivalent semiclassical formulation, valid up to second order in $\hbar$. The resulting phase-space measure and kinetic equation incorporate the quantum metric over the full phase space, including its mixed real-momentum components. We show that, in spatially inhomogeneous systems, the full phase-space quantum metric contributes to electric polarization in insulators and generates an intrinsic linear Hall response in metals. As a concrete example, we study Dirac electrons subject to a magnetic texture and a background potential that vary periodically in space. In this model, the mixed components of the phase-space metric produce a Hall contribution controlled by the relative phase between the two modulations. This phase-sensitive response can remain finite even when the conventional anomalous Hall conductivity vanishes. More broadly, our formulation enables the systematic study of equilibrium and transport responses in systems whose quantum geometry involves both position and momentum.

cond-mat.mes-hall↗

arXiv2026

Topological pumping of bimerons in spiral magnets

Precise positioning of topological defects is essential for racetrack memories, where their positions along a magnetic nanotrack encode information. Traditional methods achieve nanometric precision by engineering pinning landscapes that enforce discrete steps in defect motion. However, accessing each bit requires overcoming a depinning threshold, which increases power consumption. Here, we demonstrate that spiral magnets provide a natural ruler, enabling precise positioning of bimerons (topological spin textures analogous to skyrmions) without relying on engineered pinning sites. A rotating magnetic field couples directly to the bimeron position, displacing it by exactly one spiral period per full rotation of the field. Such quantized transport of skyrmionic textures, reminiscent of Thouless pumping, is topologically protected and remains robust against perturbations, positioning spiral magnets as a natural skyrmion racetrack. The findings establish a paradigm for topologically protected transport of spin textures.

cond-mat.str-el↗

arXiv2025

Observation of relativistic domain wall motion in amorphous ferrimagnets

Domain walls in ferrimagnets and antiferromagnets behave as relativistic sine-Gordon solitons with the spin-wave group velocity setting the ultimate velocity of domain walls and speed of magnetic devices. While this relativistic regime has been achieved in crystalline ferrimagnets, they cannot be routinely integrated in devices. To enable technological breakthroughs, relativistic dynamics must be demonstrated in easy-to-integrate ferrimagnets such as rare-earth -- transition-metal alloys. However, this scenario remains elusive due to the inherent magnetic disorder of these materials, complex spin-wave spectra, and challenges in modeling their ultrafast dynamics. Here, we demonstrate relativistic domain wall motion in amorphous ferrimagnetic GdFeCo devices operated in the proximity of the angular momentum compensation point. The current-induced domain wall velocity saturates within 10% of the spin-wave speed of 2 km/s, a behavior consistent with relativistic model of domain wall motion. Our observation of relativistic dynamics in technologically relevant ferrimagnets opens the way to magnetic devices operating at the ultimate speed limit.

cond-mat.mtrl-sci↗

arXiv2025

Merons, hedgehogs and magnetoelectric switching in spiral multiferroics

In spiral multiferroics, magnetism induces ferroelectricity, thus holding a promise for novel memory devices where an electric field switches magnetic bits. However, such a switching process, in which magnetic domain walls are moved electrically, is still poorly understood. We find multiferroic domain walls containing arrays of meron (half-skyrmion) strings with a plethora of topological defects, which profoundly affect wall dynamics. Minimum energy walls have alternating meron topological charges and move as relativistic massive particles, with velocity limited by the magnon speed. During domain nucleation, walls with non-alternating meron charges appear. Such defects result in a peculiar non-local dynamics where all the spins in the system rotate, and the wall mobility is suppressed. Meron strings possess 0D hedgehog defects, analogous to Bloch points, that pin the wall to the lattice. This fascinating interplay of magnetoelectric switching with a variety of topological defects and non-local spin dynamics opens a new playground for the electric manipulation of spins.

cond-mat.str-el↗