arXiv subjects

A. Pezo

Publications and source records attributed to A. Pezo.

9 recordsLinked to original sources

arXiv2026

First-principles prediction of chiral-phonon-induced orbital accumulation

Chiral phonons offer a route to transfer angular momentum without relying on magnetic order, but their electronic response in metals remains poorly understood from perspectives beyond spin-based scenarios. Using first-principles calculations, we show that coherent chiral lattice motion generates orbital accumulation and, through spin-orbit coupling, a smaller accompanying spin accumulation. Our approach evaluates orbital and spin expectation values directly from strain perturbed ab initio Hamiltonians in the long-wavelength limit, where the phonon perturbation is represented by symmetry adapted circular lattice distortions. We show that the response is controlled mainly by orbital character, near-degeneracies, and electron-phonon coupling, rather than by spin-orbit coupling alone. These results identify light transition metals as promising platforms for chiral-phonon-driven orbitronics.

cond-mat.mes-hall↗

arXiv2026

Unconventional views on orbitronics supported by experimental results

Emerging orbitronics assumes long-range orbital current transport, analogous to spin currents. However, recent theory and experiments challenge this view, showing rather local characters for orbital polarization and orbit-spin conversions. We study angular momentum generated by ferromagnetic resonance and thermal gradients in Ni/(Pt)Ti/Au heterostructures. The observed charge current produced is independent of Ti thickness up to 60 nm, incompatible with orbital transport in Ti. Instead, its magnitude depends on both Ti interfaces, evidencing spin-mediated transport in between after and before local orbit-spin interconversions.

cond-mat.mtrl-sci↗

arXiv2026

Emergent spin accumulation in non-Hermitian altermagnets

The recent interest in non-Hermitian (NH) systems has significantly broadened their application across condensed matter physics, offering a unique framework to explore out-of-equilibrium phenomena. Simultaneously, altermagnets have emerged as a distinct magnetic class, characterized by unconventional spin-split bands protected by crystal symmetries. In this work, we investigate the interplay between non-Hermitian dynamics and spin transport in these materials, focusing on the Edelstein effect. We demonstrate that the introduction of non-Hermiticity in $d$-wave altermagnets and $p$-wave unconventional magnets opens novel susceptibility components that are inaccessible in Hermitian counterparts. Our analysis reveals that these susceptibility channels are highly sensitive to the underlying symmetry of the order parameter. Crucially, our results show that the non-conservative nature of the system leads to the selective gain and loss of specific spin components, a phenomenon that can be tuned by the interplay between dissipation and the altermagnetic order. These components exhibit a distinct gain/loss profile that depends strictly on the N\'eel vector orientation, providing a new route for manipulating spin degrees of freedom through controlled non-conservative processes in emerging magnetic materials

cond-mat.mes-hall↗

arXiv2025

Orbital torque and efficient magnetization switching using ultrathin Co|Al light-metal interfaces: Experiments and modeling

The emergence of the orbital degree of freedom in modern orbitronics offers a promising alternative to heavy metals for the efficient control of magnetization. In this context, identifying interfaces that exhibit orbital-momentum locking and an orbital Rashba-Edelstein response to an external electric field is of primary importance. In this work, we experimentally investigate the Co/Al system and extend the study to Co/Pt/Al structures. We show that inserting ultrathin Pt layers between Co and Al can significantly modify the orbital properties, highlighting the critical role of Co/Al orbital bonding in generating orbital polarization. We further model the orbital response of these systems using semi-phenomenological approaches and linear-response theory within the framework of density-functional theory.

cond-mat.mtrl-sci↗

arXiv2025

Anatomy of torques from orbital Rashba textures: the case of Co/Al interfaces

In the context of orbitronics, the rising of the orbital angular momentum generated at light metal interfaces from orbital textures via orbital Rashba-Edelstein effects nowadays represent extraordinary alternatives to the usual heavy-metal spin-based materials. In the light of very recent experimental results [\textcolor{blue}{S. Krishnia \textit{et al.}, Nanoletters 2023, 23, 6785}], starting from state-of-the-art density functional theory simulations, we provide theoretical insights into the emergence of very strong orbital torques at the Co/Al interface location a strong orbital Rashba texture. By using linear response theory, we calculate the exerted orbital torque amplitudes, mainly of field-like intraband character, acting onto the ultrathin Co. Moreover, we show that an insertion of a single atomic plane of Pt between Co and Al is enough to suppress the effect which questions about the anatomy of the torque action clearly behaving differently than in the standard way. This work opens new routes to the engineering of spintronic devices.

cond-mat.mtrl-sci↗

arXiv2024

Inverse Rashba-Edelstein THz emission modulation induced by ferroelectricity in CoFeB/PtSe2/MoSe2//LiNbO3 systems

Spintronic Terahertz emitters, based on optically triggered spin-to-charge interconversion processes, have recently emerged as novel route towards compact and efficient THz sources. Yet, the next challenge for further technologically-relevant devices remains to modulate the emission, with low-energy consumption operation. To this aim, ferroelectric materials coupled to active spin-orbit layers such as two-dimensional transition metal dichalcogenides are suitable candidates. In this work, we present the realization of a large area heterostructure of CoFeB/PtSe2/MoSe2 on a bi-domain LiNbO3 substrate. Using THz time-domain spectroscopy, we show that the ferroelectric polarization direction induces a sizeable modulation of the THz emission. We rationalise these experimental results by using band structure and spin accumulation calculations that are consistent with an interfacial spin-to-charge conversion mediated by inverse Rashba-Edelstein effect at the MoSe2/PtSe2 interface and being tuned by ferroelectricity in the adjacent LiNbO3 surface. This work points out the relevance of field effect spin-orbit architectures for novel THz technologies.

cond-mat.mtrl-sci↗

arXiv2023

Orbital diffusion, polarization and swapping in centrosymmetric metals

We propose a general theory of charge, spin, and orbital diffusion based on Keldysh formalism. Our findings indicate that the diffusivity of orbital angular momentum in metals is much lower than that of spin or charge due to the strong orbital intermixing in crystals. Furthermore, our theory introduces the concept of spin-orbit polarization by which a pure orbital (spin) current induces a longitudinal spin (orbital) current, a process as efficient as spin polarization in ferromagnets. Finally, we find that orbital currents undergo momentum swapping, even in the absence of spin-orbit coupling. This theory establishes several key parameters for orbital transport of direct importance to experiments.

cond-mat.mes-hall↗

arXiv2023

Charge pumping with strong spin-orbit coupling: Fermi surface breathing, Berry curvature, and higher harmonic generation

Spin and charge pumping induced by a precessing magnetization has been instrumental to the development of spintronics. Nonetheless, most theoretical studies so far treat the spin-orbit coupling as a perturbation, which disregards the competition between exchange and spin-orbit fields. In this work, based on Keldysh formalism and Wigner expansion, we develop an adiabatic theory of spin and charge pumping adapted to systems with arbitrary spin-orbit coupling. We apply this theory to the magnetic Rashba gas and magnetic graphene cases and discuss the pumped ac and dc current. We show that the pumped current possesses both intrinsic (Berry curvature-driven) and extrinsic (Fermi surface breathing-driven) contributions, akin to magnetic damping. In addition, we find that higher harmonics can be generated under large-angle precession and we propose a couple of experimental setups where such an effect can be experimentally observed.

cond-mat.mes-hall↗

arXiv2018

Braiding of edge states in narrow zigzag graphene nanoribbons: effect of the third neighbors hopping

We study narrow zigzag graphene nanoribbons (ZGNRs), employing density functional theory (DFT) simulations and the tight-binding (TB) method. The main result of these calculations is the braiding of the conduction and valence bands, generating Dirac cones for non-commensurate wave vectors $\vec{k}$. Employing a TB Hamiltonian, we show that the braiding is generated by the third-neighbor hopping (N3). We calculate the band structure, the density of states and the conductance, new conductance channels are opened, and the conductance at the Fermi energy assumes integer multiples of the quantum conductance unit $G_{o} = 2e^{2}/h$. We also investigate the satisfaction of the Stoner criterion by these ZGNRs. We calculate the magnetic properties of the fundamental state employing LSDA (spin-unrestricted DFT) and we confirm that ZGNRs with $N=(2,3)$ do not satisfy the Stoner criterion and as such the magnetic order could not be developed at their edges. These results are confirmed by both tight-binding and LSDA calculations.

cond-mat.mes-hall↗