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Ousmane Ly

Publications and source records attributed to Ousmane Ly.

12 recordsLinked to original sources
arXiv2026

An Energy Integration Free Kubo-Bastin Formula Decomposition

Kubo formulae play a central role in modern spintronics and condensed matter physics, serving as the foundational ground for studying transport responses in the linear regime. In this work, we propose a reformulation of the widely used Kubo-Bastin decompositions that eliminates the need for numerical energy integration. By performing these integrations analytically for generic periodic systems, our approach drastically reduces computational cost and simplifies the evaluation of transport coefficients.

cond-mat.mes-hall↗
arXiv2026

Unconventional alternating out-of-plane spin polarization in the coplanar kagome antiferromagnet

The emergence of spin-polarized currents in nonrelativistic platforms continues to attract significant interest in spintronics. Here we demonstrate that a noncollinear kagome antiferromagnet can generate an alternating out-of-plane spin polarization originating from the spin chirality of the magnetic unit cell, in the absence of relativistic spin--orbit coupling. Under spatial confinement, the system develops distinct real-space spin separation patterns whose structure is governed by the symmetry of the lattice termination. In particular, breaking the transverse mirror symmetry of the ribbon produces an altermagnetic-like spin splitting in the band structure. Furthermore, we uncover a spin--edge locking mechanism in which propagating edge states acquire an unconventional spin polarization. These results highlight how magnetic symmetry and confinement can generate spin-polarized transport in coplanar antiferromagnets without relying on relativistic interactions.

cond-mat.mes-hall↗
arXiv2026

High-Harmonic Spin and Charge Pumping in Altermagnets

We report the emergence of highly nonlinear spin and charge pumping in an altermagnetic system driven by magnetic dynamics. The non-relativistic spin-momentum coupling inherent to altermagnets (AMs) generates a giant momentum dependent spin splitting, leading to strong spin-flip scattering in the presence of a precessing magnetic order driving the altermagnetic system out of equilibrium. Our simulations reveal the emission of hundreds of harmonics under realistic conditions, with amplitudes far exceeding those obtained in light-driven schemes. Notably, in contrast to ferromagnetic and conventional antiferromagnetic systems, where nonlinear emission typically requires additional spin-orbit coupling, AMs intrinsically support high-harmonic spin and charge pumping. These results identify altermagnetic systems as a promising platform for efficient THz emitters and highly nonlinear spintronic devices.

cond-mat.mes-hall↗
arXiv2026

A Purely Magnetic Route to High-Harmonic Spin Pumping

Spin pumping provides a fundamental route for dynamical spin transport, yet in its conventional form it produces only linear spin responses at the driving frequency. Recent studies have shown that spin-orbit coupling (SOC) can lift these restrictions and enable strongly nonlinear spin and charge currents. Here we propose a distinct mechanism for high-harmonic spin pumping that operates independently of spin-orbit interactions. We demonstrate that purely magnetic structures can sustain high-harmonic spin currents when an additional static magnetic order parameter is introduced perpendicular to the cone axis of a precessing magnetization. This secondary magnetic order qualitatively reshapes the dynamical response, giving rise to a cascade of higher harmonics in the pumped spin current in the absence of SOC. Our results establish a SOC-independent route to ultrafast and nonlinear spin pumping rooted solely in magnetic structure and dynamics.

cond-mat.mes-hall↗
arXiv2026

Generative Artificial Intelligence, Musical Heritage and the Construction of Peace Narratives: A Case Study in Mali

This study explores the capacity of generative artificial intelligence (Gen AI) to contribute to the construction of peace narratives and the revitalization of musical heritage in Mali. The study has been made in a political and social context where inter-community tensions and social fractures motivate a search for new symbolic frameworks for reconciliation. The study empirically explores three questions: (1) how Gen AI can be used as a tool for musical creation rooted in national languages and traditions; (2) to what extent Gen AI systems enable a balanced hybridization between technological innovation and cultural authenticity; and (3) how AI-assisted musical co-creation can strengthen social cohesion and cultural sovereignty. The experimental results suggest that Gen AI, embedded in a culturally conscious participatory framework, can act as a catalyst for symbolic diplomacy, amplifying local voices instead of standardizing them. However, challenges persist regarding the availability of linguistic corpora, algorithmic censorship, and the ethics of generating compositions derived from copyrighted sources.

cs.SD↗
arXiv2024

Carbon nanotube as quantum point contact valley-filter and valley-splitter

The electrical characteristics of a carbon nanotube can be significantly modified by applying elastic strain. This study focuses on exploring this phenomenon in a single-walled carbon nanotube (SWNT) using tight-binding transport calculations. The results indicate that, under specific strains, an armchair SWNT can act as a filter, separating the two valley electrons K and Kp. Notably, when subjected to deformation, the SWNT exhibits intriguing behaviors, including a quantized conductance profile that varies with the strength of the strain. Consequently, precise control of the width of the quantized plateaus allows for the generation of a polarized valley current. Furthermore, when both K-types are conducted, the strain is demonstrated to completely separate them, directing each K-type through a distinct pathway.

cond-mat.mes-hall↗
arXiv2023

Pseudo Electric Field and Pumping Valley Current in Graphene Nano-bubbles

The extremely high pseudo-magnetic field emerging in strained graphene suggests that an oscillating nano-deformation will induce a very high current even without electric bias. In this paper, we demonstrate the sub-terahertz (THz) dynamics of a valley-current and the corresponding charge pumping with a periodically excited nano-bubble. We discuss the amplitude of the pseudo-electric field and investigate the dependence of the pumped valley current on the different parameters of the system. Finally, we report the signature of extra-harmonics generation in the valley current that might lead to potential modern devices development operating in the nonlinear regime

cond-mat.mes-hall↗
arXiv2023

Scanning Gate Microscopy response for local tip potentials beyond perturbation theory

We propose an analytical formulation for the Scanning Gate Microscopy (SGM) response to local tips with arbitrary strength in two terminal nano-structures. The real space resolved conductance is expressed in terms of the unperturbed quantities underlying the scattering problem. Providing a non-dynamical approach for obtaining the SGM maps, the proposed expression enables for a significant reduction in the computational cost of SGM response calculations. This feature is particularly advantageous for deep learning-based approaches which have been recently proposed for accessing local properties and disorder landscapes from conductance measurements. This opens up new possibilities for the SGM technique and holds exciting prospects for quantum transport. Further, the formula's versatility extends beyond this specific application, offering a straightforward and computationally efficient method for obtaining the SGM response in a more general context.

cond-mat.mes-hall↗
arXiv2023

Scaling Laws of Magnetically Driven High-order Harmonic Generation in Spin-Orbit Coupled Systems

We investigate the scaling behavior of high harmonic generation (HHG) driven by magnetic dynamics in spin-orbit coupled systems. In contrast to optically driven HHG--where the harmonic cutoff scales as $\omega^{-3}$ with the driving frequency $\omega$--our time-dependent quantum transport simulations reveal a qualitatively distinct scaling law for magnetically driven HHG in the presence of Rashba spin-orbit interaction: the harmonic cutoff $n_{\mathrm{max}}$ scales as $\omega^{-1}$. This fundamental difference arises from distinct excitation mechanisms--namely, spin-flip transitions driven by vectorial magnetic precession, as opposed to scalar electric fields. Furthermore, we demonstrate that the precession cone angle $\theta$ serves as a crucial control parameter. Increasing $\theta$ broadens the harmonic bandwidth, with peak emission achieved for nearly in-plane magnetic dynamics. Our findings establish magnetically driven HHG as a robust and tunable mechanism for nonlinear spin transport, governed by unique scaling laws with potential applications in ultrafast spintronic technologies.

cond-mat.mes-hall↗
arXiv2022

Noncollinear antiferromagnetic textures driven high harmonic generation from magnetic dynamics in the absence of spin-orbit coupling

We demonstrate the generation of high order harmonics in carrier pumping from precessing ferromagnetic or antiferromagnetic orders, excited via magnetic resonance, in the presence of topological antiferromagnetic textures. This results in an enhancement of the carrier dynamics by orders of magnitude. Interestingly, the generation process occurs in an intrinsic manner, and is solely governed by the interplay between the s-d exchange coupling underlying the noncollinear antiferromagnetic order and the dynamical s-d exchange parameter of the magnetic drive. Therefore, the relativistic spin-orbit interaction is not required for the emergence of high harmonics in the pumped currents. Accordingly, the noncollinear topological antiferromagnetic order is presented as an alternative to spin-orbit interaction for the purpose of harnessing high harmonic emission in carrier pumping. Our proposal initiates a tantalizing perspective for the exploitation of topological magnetic textures in the context of the highly active domain of ultrafast spintronics.

cond-mat.mes-hall↗
arXiv2017

Partial local density of states from scanning gate microscopy

Scanning gate microscopy images from measurements made in the vicinity of quantum point contacts were originally interpreted in terms of current flow. Some recent work has analytically connected the local density of states to conductance changes in cases of perfect transmission, and at least qualitatively for a broader range of circumstances. In the present paper, we show analytically that in any time-reversal invariant system there are important deviations that are highly sensitive to imperfect transmission. Nevertheless, the unperturbed partial local density of states can be extracted from a weakly invasive scanning gate microscopy experiment, provided the quantum point contact is tuned anywhere on a conductance plateau. A perturbative treatment in the reflection coefficient shows just how sensitive this correspondence is to the departure from the quantized conductance value and reveals the necessity of local averaging over the tip position. It is also shown that the quality of the extracted partial local density of states decreases with increasing tip radius.

cond-mat.mes-hall↗