arXiv subjects

Jairo Sinova

Publications and source records attributed to Jairo Sinova.

At least 19 recordsLinked to original sources

arXiv2026

Anti-spin Laue groups: classification of anti-altermagnets and their representative minimal models

Anti-altermagnets exhibit odd-parity nonrelativistic spin splitting, yet unlike even-parity altermagnets, their momentum-space symmetries lack a reduced classification analogous to spin Laue groups. Here, we introduce anti-spin Laue groups, organized into three distinct classes, and identify 21 groups describing the odd-parity partial wave character of this unconventional class. Together with the 10 spin Laue groups of altermagnets, they complete the classification of nonrelativistic unconventional magnets with collinear momentum-space spin polarization. Anti-spin Laue groups also provide a many-to-one reduction of spin space (point) groups by retaining only their action on the collinear momentum-space spin polarization, thereby directly encoding the symmetry-enforced nodal spin-splitting character. Based on this we develop a systematic model-construction algorithm yielding minimal, material-oriented four-band models. This framework places odd- and even-parity unconventional magnets on equal footing within a unified momentum-space symmetry description.

cond-mat.mtrl-sci↗

arXiv2026

Rolling Two-Dimensional Collinear Magnets into Chiral Nanotubes with $p$-Wave Magnetism

$p$-wave magnets are noncollinear compensated magnetic systems that exhibit nonrelativistic antisymmetric spin splitting in momentum space. Their odd-parity spin symmetry enables unconventional spintronic functionalities, including highly efficient charge-to-spin conversion via the Edelstein effect. An outstanding question is whether such magnetic phases can emerge from simple and broadly accessible magnetic building blocks rather than from intrinsically noncollinear magnetic orders. Here, we show that rolling two-dimensional collinear magnets -- ferromagnets, antiferromagnets, and altermagnets -- into nanotubes generates a rich spin-symmetry landscape controlled by curvature, chirality, and magnetic order. Remarkably, chiral nanotubes hosting radial or tangential coplanar spin textures generically realize $p$-wave magnetism irrespective of the underlying collinear parent phase. The emergent odd-parity spin symmetry manifests itself in both electronic and magnonic spectra through antisymmetric $p$-wave spin splitting. Our results establish magnetic nanotubes as a versatile platform for engineering unconventional $p$-wave magnetism and predict a nonrelativistic Edelstein response that exceeds conventional spin-orbit-driven charge-to-spin conversion by more than an order of magnitude.

cond-mat.mes-hall↗

arXiv2026

Floquet-induced anisotropic magnetoresistance and anomalous Hall effect in 2D $d$-wave altermagnets with Rashba spin-orbit coupling

Altermagnets (AMs) combine momentum-dependent spin splitting with zero net magnetization, making them promising for spintronics. Periodic driving enables dynamic symmetry engineering beyond static, material-specific control. We show that Floquet engineering in 2D $d$-wave AMs with out-of-plane N\'eel order and Rashba spin-orbit coupling unlocks equilibrium-forbidden transport responses. Monochromatic driving produces purely out-of-plane magnetization, yielding longitudinal anisotropic magnetoresistance (AMR) and an anomalous Hall effect, whereas bichromatic driving generates both in-plane and out-of-plane magnetizations and additionally activates transverse AMR via the second harmonic of the secondary beam. Comparable static magnetic fields would require hundreds of tesla, avoided in Floquet driving. These effects persist across linear, circular, and mixed light polarizations and are tunable via light parameters. Our results establish multi-color Floquet engineering for controlling magnetization and symmetry-protected transport in AMs.

cond-mat.mtrl-sci↗

arXiv2026

Nonlinear Magnon Magnetic Moment Transport in Triangular-Lattice f-Wave Antialtermagnets

We study the spin excitations in the frustrated coplanar 120-degree ground state of the triangular-lattice Heisenberg antiferromagnet and demonstrate that they carry a magnetic moment perpendicular to the plane in which the spins order, despite the ground-state sublattice moments having no out-of-plane component. The symmetry of the momentum dependence of the magnetic moment and energy of the magnons renders the system an odd-parity f-wave magnet. Extending this model to a stack of antiferromagnetically coupled triangular layers provides a realization of magnons in a three-dimensional f-wave antialtermagnet. We show that nonlinear thermal transport effects of magnons, such as Edelstein and spin-splitter effects, provide clear experimental signatures of magnons in f-wave antialtermagnets.

cond-mat.str-el↗

arXiv2026

Giant orbital magnetoresistance in the antiferromagnet CoO driven by dynamic orbital angular momentum interaction

Recent predictions of orders of magnitude larger orbital current effects compared to spin currents have attracted significant interest. However, the full potential of giant orbital currents remains to be fully harnessed, since so far, the orbital currents need to be converted into spin currents before they can interact with the static magnetization that is dominated by spin angular momentum in conventional magnets. By using a magnet dominated by orbital angular momentum, we demonstrate a more than fifty-fold enhancement in orbital Hall magnetoresistance in CoO/Cu*, compared to conventional CoO/Pt. This is found to be driven by a unique interaction between dynamic orbital angular momentum from surface oxidized Cu* (i.e., the orbital current) and the static orbital angular momentum which constitutes the magnetic moments in the antiferromagnetic insulator CoO. A distinctive scattering mechanism for orbital currents at the CoO interface leads to a sign reversal in orbital magnetoresistance in CoO/Cu* compared to CoO/Pt. Our results show how by using orbital angular momentum-dominated materials such as CoO, we can harness the benefits of giant orbital currents that have not been possible using conventional spin-dominated magnets, for orbitronics-based devices, offering unprecedented energy efficiency for operations of antiferromagnets that combine ultimate stability with THz dynamics.

cond-mat.mtrl-sci↗

arXiv2026

Odd-Parity-Wave Magnons and Nonrelativistic Thermal Edelstein Effect

Odd-parity-wave magnets are noncollinear compensated magnets with spin-split band structure in the absence of spin-orbit coupling and dipolar interactions. In contrast to altermagnets, their spin-polarized band structure breaks inversion symmetry, but preserves time-reversal symmetry rendering their spin texture odd in momentum space. Here, we study the spin dynamics of the magnetic texture and compute the band structure and spin polarization of magnons. We present minimal spin models of noncoplanar odd-parity-wave magnets purely stabilized by exchange interactions that host p- and f-wave spin textures for the magnetic excitations. We demonstrate that two of these models exhibit collinear spin textures, i.e., the magnon spin polarization is restricted to a global (quantization) axis independent of the momentum giving rise to single-component odd-parity-wave magnetism, previously associated primarily with coplanar ground states. Finally, the nonrelativistic magnonic thermal Edelstein effect -- a nonequilibrium magnetization induced by a temperature gradient -- is shown to exist for p-wave magnets in linear response and inherits its anisotropic angular dependence from the partial-wave character of the spin-polarized band structure. Our findings suggest that insulating odd-parity-wave magnets are promising candidates for magnon spintronics applications.

cond-mat.mes-hall↗

arXiv2026

Emergent altermagnetism at surfaces of antiferromagnets: full symmetry classification and material identification

We demonstrate the emergence of altermagnetism at the surfaces of antiferromagnets, vastly expanding the number of material candidates with altermagnetic characteristics and establishing a route towards two-dimensional altermagnetism through surface-induced symmetry breaking. We do so by developing a surface spin group formalism that fully classifies all surface magnetic states and identifies altermagnetic surface spin groups that can arise at the surfaces of antiferromagnets. We use this formalism to identify over 150 antiferromagnetic entries from the MAGNDATA database with at least one altermagnetic surface, often times with multiple such surfaces in the same material, and clarify the role of surface roughness and terraces. We illustrate this emergent phenomenon in a realistic Lieb lattice-based minimal model and present ab initio calculations on two representative material candidates, $\text{NaMnP}$ and $\text{FeGe}_2$, exhibiting $d$-wave and $g$-wave surface altermagnetism, respectively. Our theory naturally resolves the contradiction of recent experimental reports of $d$-wave spin splitting from ARPES measurements on metallic Lieb lattice compounds such as KV$_2$Se$_2$O that have been shown to be antiferromagnetic in the bulk. Hence, we establish a new paradigm for generating effectively two-dimensional altermagnetism by functionalizing the abundant material class of collinear antiferromagnets as viable platforms for controlled surface altermagnetism.

cond-mat.mtrl-sci↗

arXiv2026

Engineering altermagnetic symmetry to enable anomalous Hall response in Cr$_{1-x}$Mn$_x$Sb

Altermagnets are a promising class of materials for spintronic applications. However, compounds that simultaneously combine the symmetry required to support an anomalous Hall effect with good metallic conductivity and magnetic ordering temperatures well above room temperature have remained elusive. Here, we demonstrate that partial substitution of Cr by Mn in epitaxial CrSb(100) thin films provides a viable route to engineer the combined structural and magnetic symmetry necessary to enable an otherwise symmetry-forbidden anomalous Hall effect. We systematically explore the magnetic phase diagram of Cr(Mn)Sb thin films including neutron diffraction. This allows us to identify a magnetic symmetry that supports the anomalous Hall effect, which we demonstrate in Cr(0.75)Mn(0.25)Sb. Guided by Landau theory, we model the field-driven reorientation of the Neel vector and the resulting anomalous Hall response, achieving good qualitative agreement with the experimental observations.

cond-mat.mtrl-sci↗

arXiv2025

Direct demonstration of time-reversal-symmetry-breaking spin injection from a compensated magnet

The injection, propagation and detection of spin currents are essential physical processes in spintronics. So far, the separation of charge and spin currents was facilitated by the electrical spin injection from a ferromagnet (FM) or the injection by a relativistic spin Hall effect. The devices employed are lateral spin valves comprising spatially separated injection and detection electrodes, connected by a spin-propagation channel. The time-reversal symmetry (TRS) breaking FM spin injection is realized in a geometry with an electrical bias applied between the injection electrode and the channel and is modelled by a conserved spin-polarized drift current. In contrast, the spin injection by the T-symmetric relativistic spin Hall mechanism is driven by an electrical bias applied across the injection electrode alone, and is modelled by a non-conserved spin current transverse to the applied bias. In this work, we use a lateral spin valve with a Mn5Si3 injection electrode to directly demonstrate a TRS-breaking spin injection from a compensated magnet with a vanishing net magnetization. Specifically, the TRS-breaking is demonstrated by the fact that switching between time-reversed states of the compensated magnet changes the detected spin signal. Moreover, the TRS-breaking nature of the spin injection is observed in both experimental geometries with the different electrical biasing, while using the same detection electrode. We show that this unconventional spin-injection is consistent with different magnitudes and propagation angles of electrical currents in the spin-up and spin-down channel in a d-wave altermagnet. Here our symmetry analysis and first-principles calculations are based on the compensated collinear altermagnetic order which has provided a comprehensive microscopic interpretation of earlier structural, magnetic, and anomalous Hall and Nernst measurements in Mn5Si3 thin films.

cond-mat.mes-hall↗

arXiv2025

Quantum-impurity sensing of altermagnetic order

Quantum sensing with individual spin defects has emerged as a versatile platform to probe microscopic properties of condensed matter systems. Here we demonstrate that quantum relaxometry with nitrogen-vacancy (NV) centers in diamond can reveal the anisotropic spin dynamics of altermagnetic insulators together with their characteristic spin polarised bands. We show that the distance and orientation dependent relaxation rate of a nearby quantum impurity encodes signatures of momentum space anisotropy in the spin diffusion response, a hallmark of altermagnetic order. This directional sensitivity is unprecedented in the landscape of quantum materials sensing, and it enables the distinction of altermagnets from conventional antiferromagnets via local, noninvasive measurements. Our results could spark new NV-sensing experiments on spin transport and symmetry breaking in altermagnets, and highlight the role of NV orientation to probe anisotropic phenomena in condensed matter systems.

cond-mat.mes-hall↗

arXiv2025

Switchable Exchange Bias Resulting from Correlated Domain Structures in Orthogonally Coupled Antiferromagnet/Ferromagnet van der Waals Heterostructures

Van der Waals (vdW) magnetic heterostructures offer a versatile platform for engineering interfacial spin interactions with atomic precision, enabling nontrivial spin textures and dynamic behaviors. In this work, we report robust asymmetric magnetization reversal and exchange bias in Fe3GeTe2 (FGT), driven by interlayer exchange coupling with the A-type antiferromagnet CrSBr. Despite the orthogonal magnetic anisotropies out-of-plane easy axis in FGT and in-plane in CrSBr, we observe a strong interfacial exchange interaction that gives rise to pronounced and switchable exchange bias and asymmetric switching in FGT, persisting up to the N\'eel temperature of CrSBr (132 K) as revealed by anomalous Hall effect measurements. We uncover the microscopic origin of this behavior through cross-sectional magnetic imaging of the domain structure using off-axis electron holography. The results reveal that the asymmetric switching and exchange bias arise from the influence of CrSBr on the domain configuration of FGT, where the in-plane antiferromagnetic state of CrSBr promotes the formation of stripe-like domain structures in FGT with circular rotation of magnetization in the cross-sectional bc plane defined by the easy axes of both FGT and CrSBr. These findings elucidate the mechanism of exchange bias in orthogonally coupled van der Waals systems and demonstrate a pathway for stabilizing three-dimensional domain structures in ferromagnets through interfacial exchange interactions.

cond-mat.mtrl-sci↗

arXiv2025

Symmetry, microscopy and spectroscopy signatures of altermagnetism

Altermagnetism is a collinear compensated magnetically-ordered phase with a d, g or i-wave anisotropy and alternating spin polarization of the electronic structure in the position and momentum space. Its recent discovery was in part motivated by the research of compensated magnets towards highly scalable spintronic technologies. Simultaneously, altermagnetism shares the anisotropic higher-partial-wave nature of ordering with unconventional superfluid phases which have been at the forefront of research for the past several decades. These examples illustrate the interest in altermagnetism from a broad range of science and technology perspectives. After summarizing the diverse research context, we turn the focus of this review to the symmetry, microscopy and spectroscopy signatures of altermagnetism. We start from the description of spontaneously broken and retained symmetries which delineate the compensated altermagnetic ordering as a distinct magnetic phase. Next we focus on microscopic signatures and ordering mechanism of the altermagnetic phase. We highlight crystal-structure realizations of a characteristic ferroic order of anisotropic higher-partial-wave components of atomic-scale spin densities in altermagnets, ranging from weakly-interacting metals to strongly correlated insulators. The symmetry and microscopy signatures of altermagnetism are directly reflected in spin-dependent electronic spectra and responses. We review salient band-structure features originating from the altermagnetic ordering, and from its interplay with spin-orbit coupling and topological phenomena. Throughout the review we compare altermagnetism to traditional ferromagnetism and Neel antiferromagntism, and to the currently intensely explored magnetic phases with non-collinear symmetry-protected compensated spin orders. We accompany the theoretical discussions by references to relevant experiments.

cond-mat.mtrl-sci↗

arXiv2025

Strain controlled g- to d-wave transition in altermagnetic CrSb

The possibility of a strain-induced transformation from $g$-wave to $d$-wave altermagnetism was recently recently proposed for MnTe using a $k\cdot p$ perturbative model. In this work, we demonstrate such a transition in CrSb for a wider array of strains, using a combination of a minimal model and first-principles calculations. Starting from a symmetry perspective, we analyze the spin elastoconductivity tensor, and determine the strain types which allow for a change in the altermagnetic symmetry. We obtain three strain directions, which allow for a $d$-wave type splitting, and one in which a net magnetic moment emerges. Using first-principles calculations in the absence of spin-orbit coupling (SOC), we confirm these symmetry predictions. Furthermore, these results do not alter qualitatively in the presence of SOC. Finally, we reveal that the resulting spin currents give rise to a spin-splitter effect of up to 5\% under realistic strains of 1\%, confirming strain as a powerful tool for tuning altermagnetic properties.

cond-mat.mtrl-sci↗

arXiv2025

Optical signatures of bulk g-wave altermagnetism in MnTe

For planar d-wave altermagnets, it has been shown that a spin polarization can be induced in a controlled fashion by ultrashort-pulse excitation, even though the material is magnetically compensated. Here, we theoretically analyze the response of the prototypical bulk $g$-wave altermagnet $\alpha$-MnTe to linearly polarized ultrashort pulses. We demonstrate how the electronic spin response in $\alpha$-MnTe exhibits different symmetry characteristics by calculating the excited electron distributions based on ab initio band structure data. These characteristics depend not only on the nodal planes of the bulk g-wave altermagnet, but also on the excitation pulse. We present a simple procedure to analyze the excited-state characteristics via two-dimensional cuts through the three-dimensional Brillouin zone, which can be used as guidance to present-day magneto-optical techniques.

cond-mat.mtrl-sci↗

arXiv2025

Spin demons in d-wave altermagnets

Demons are a type of plasmons, which consist of out-of-phase oscillations of electrons in different bands. Here, we show that $d$-wave altermagnets, a recently discovered class of collinear magnetism, naturally realize a spin demon, which consists of out-of-phase movement of the two spin species. The spin demon lives outside of the particle-hole continuum of one of the spin species, and is therefore significantly underdamped, reaching quality factors of $>10$. We show that the spin demon carries a magnetic moment, which inherits the $d$-wave symmetry. Finally, we consider both three and two dimensional $d$-wave altermagnets, and show that spin demons exists in both.

cond-mat.str-el↗

arXiv2025

Chiral magnetic excitations and domain textures of g-wave altermagnets

Altermagnets (AMs) constitute a novel class of spin-compensated materials in which opposite-spin sublattices are connected by a crystal rotation, causing their electronic iso-energy surfaces to be spin-split. While cubic and tetragonal crystal symmetries tend to produce AMs in which the splitting of electronic iso-energy surfaces has $d$-wave symmetry, hexagonal AMs, such as CrSb and MnTe, are $g$-wave AMs. Here we investigate the purely magnetic modes and spin-textures of $g$-wave AMs and show that they are drastically different for easy-axial (CrSb) and easy-planar (MnTe) materials. We show that in CrSb the splitting of the chiral magnon branches possesses $g$-wave symmetry, with each branch carrying a fixed momentum-independent magnetic moment. The altermagnetic splitting is not affected by the easy-axial anisotropy and is the same as that in the nonrelativistic limit. The magnon splitting of MnTe, however, does not strictly possess $g$-wave symmetry due to its easy-planar anisotropy. Instead, the magnetic moment of each branch becomes momentum-dependent, with a distribution that is of $g$-wave symmetry. To generalize the concept of the altermagnetic splitting beyond the nonrelativistic limit, we introduce alternative, directly observable splitting parameter which comprises both the magnon eigenenergy and its magnetic moment and possesses the $g$-wave symmetry in both easy-axial and easy-planar cases. The associated altermagnetic domain walls in easy-axial CrSb possess a net magnetization with an amplitude that depends on their orientation.

cond-mat.str-el↗

arXiv2025

Atomic Altermagnetism

Altermagnetism has been recently experimentally verified by photoemission mapping of the spin order in momentum space in MnTe and CrSb, which feature two anisotropic sublattices with antiparallel magnetic dipole moments. In this work, we explicitly demonstrate the presence of an even-parity ferroically ordered non-dipolar spin density on the atomic sites, i.e. atomic altermagnetism, in MnTe, $La_2O_3Mn_2Se_2$ and $Ba_2CaOsO_6$. We do so through spin-symmetry analysis and partial-wave decomposition of the spin density obtained by first-principles calculations. In MnTe we show a ferroically ordered g-wave form factor in the spin density around the Mn site. In the $A_2O_3M_2Se_2$ family (A= La, Sr and M= Mn, Fe, Co), we show that there is a ferroically ordered d-wave form factor coexisting with the antiferroic magnetic dipoles in the M site, while the O site shows no dipole but a pure d-wave atomic spin density. In the Mott-insulating candidate $Ba_2CaOsO_6$, as a key result, we reveal a pure form of atomic altermagnetism - absent of any dipolar sublattice order. This highlights that the altermagnetic order can exist without a N\'eel vector formed by antiferroic dipole moments on an even number of crystal sublattices, underlining its distinction from collinear N\'eel antiferromagnetic order. Our calculations predict that $La_2O_3Mn_2Se_2$ and $Ba_2CaOsO_6$ can exhibit giant spin-splitter angles of up to 42{\deg} and 26{\deg} respectively, thus demonstrating the possibility of large altermagnetic responses without requiring the staggered N\'eel order of local dipole moments.

cond-mat.mtrl-sci↗

arXiv2025

Spontaneous magnon decays from nonrelativistic time-reversal symmetry breaking in altermagnets

Quasiparticles are central to condensed matter physics, but their stability can be undermined by quantum many-body interactions. Magnons, quasiparticles in quantum magnets, are particularly intriguing because their properties are governed by both real and spin space. While crystal symmetries may be low, spin interactions often remain approximately isotropic, limiting spontaneous magnon decay. Textbook wisdom holds that collinear Heisenberg magnets follow a dichotomy: ferromagnets host stable magnons, while antiferromagnetic magnons may decay depending on dispersion curvature. Up to now, relativistic spin-orbit coupling and noncollinear order that connect spin space to real space, were shown to introduce more complex magnon instability mechanisms. Here, we show that even in nonrelativistic isotropic collinear systems, this conventional dichotomy is disrupted in altermagnets. Altermagnets, a newly identified class of collinear magnets, exhibit compensated spin order with nonrelativistic time-reversal symmetry breaking and even-parity band splitting. Using kinematic analysis, nonlinear spin-wave theory, and quantum simulations, we reveal that even weak band splitting opens a decay phase space, driving quasiparticle breakdown. Additionally, d-wave altermagnets form a rare ``island of stability'' at the Brillouin zone center. Our findings establish a quasiparticle stability trichotomy in collinear Heisenberg magnets and position altermagnets as a promising platform for unconventional spin dynamics.

cond-mat.str-el↗