arXiv subjects

Pierre-Maurice Piel

Publications and source records attributed to Pierre-Maurice Piel.

3 recordsLinked to original sources

arXiv2026

Optical Readout of Reconfigurable Layered Magnetic Domain Structure in CrSBr

The van der Waals magnetic semiconductor CrSBr combines multistable magnetic order with strong light--matter coupling, enabling optical access to a rich and reconfigurable layered magnetic domain structure. A purely optical, non-destructive, and non-contact readout of layered magnetic configurations is realized here by magneto-reflectance measurements and interpreted using an optical multilayer model. The magnetic state is tunable by applied magnetic fields and by interfacing CrSBr with the antiferromagnet MnPS$_3$. Applying an external magnetic field along the easy axis drives the hysteretic antiferromagnetic--to--ferromagnetic transition, which is not universally binary but instead develops through a cascade of intermediate magnetic configurations whose multiplicity and stability scale systematically with layer thickness and can be tailored by magnetic interfaces. The intertwined optical and magnetic properties of CrSBr provide a readout mechanism for information encoded in and processed through its magnetic configuration that is compatible with modern on- and off-chip photonic and electronic technologies. These properties identify CrSBr as a promising platform for intelligent matter and for spin-optoelectronics, in particular for neuromorphic architectures that can learn and evolve in response to changing environments.

cond-mat.mes-hall↗

arXiv2026

Dielectric Tensor of CrSBr from Spectroscopic Imaging Ellipsometry

Chromium sulfur bromide (CrSBr) is a magnetic van der Waals semiconductor with a direct bandgap and pronounced anisotropy in its electronic, optical, spin and lattice degrees of freedom. Here, we employ spectroscopic imaging ellipsometry (SIE) and Mueller-matrix analysis to determine the full dielectric tensor of paramagnetic CrSBr thin films. Our measurements reveal optical anisotropy, characterized by three distinct diagonal components of the dielectric tensor. The in-plane elements are dominated by prominent excitonic resonances polarized along the two main crystallographic axes. Two main excitonic bands (A and B excitons) centered around 1.3eV and 1.7eV, respectively, are identified; the A-exciton polarized along the b-crystallographic direction, whereas the B-exciton appears to consist of two nearly degenerate contributions polarized along two orthogonal in-plane crystal axes. These results provide fundamental insight into anisotropic light-matter interactions in CrSBr, relevant for future spin-optoelectronic and photonic applications.

cond-mat.mtrl-sci↗

arXiv2024

Quadratic optical response of CrSBr controlled by spin-selective interlayer coupling

The optical properties of the layered magnet CrSBr are dominated by intralayer excitons: the antiferromagnetic order between the layers makes layer-to-layer charge hopping, and therefore interlayer excitons, spin-forbidden. An external magnetic field, however, continuously drives the magnetic order towards layer-to-layer ferromagnetic, which opens spin-allowed charge-transfer channels between the layers. Here we elaborate how their admixture changes the composition and nature of the excitons, leading to an extension over many layers, and causes a quadratic red-shift with respect to the external magnetic field. We address these effects by ab-initio $GW$-BSE calculations as a function of magnetic field and cast the data into a minimal four-band model to elucidate the interplay between the various interaction and coupling mechanisms. Our findings should be generally valid for antiferromagnetic layered magnets with and without external magnetic fields, and moreover for any couple of layers with different spin directions. Our insights help to systematically address excitons and predict their optical signatures in such systems.

cond-mat.mes-hall↗