arXiv subjects

Rodrigo Jaeschke-Ubiergo

Publications and source records attributed to Rodrigo Jaeschke-Ubiergo.

17 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

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

Emergence and Detection of Surface altermagnetism in KV$_2$Se$_2$O

We demonstrate the recent concept of emergent surface altermagnetism through its unique signatures in \KVSO. We show that for bulk antiferromagnetically ordered \KVSO, the (001) surface exhibits $d$-wave altermagnetism. Our results fully explain the recent seemingly contradicgting experimental evidence, independently showing both an antiferromagnetically ordered bulk from neutron diffraction, and $d$-wave spin splitting from photoemission spectroscopy. To fully verify this conecept, we predict, as a key experimental signature, a large nonlinear Edelstein response, which is localized at the surface, and follows the $d$-wave altermagnetic symmetry. These results are not only relevant for the metallic and room-temperature magnet \KVSO, but also for several other Lieb lattice systems. Our work expands the pool of techniques that can be used to detect altermagnetism emerging at the surfaces of antiferromagnets.

cond-mat.str-el↗

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

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

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↗

arXiv2025

Non-relativistic linear Edelstein effect in helical EuIn2As2

Motivated by the ongoing interest in understanding the actual magnetic ground state of the promising axion insulator candidate EuIn2As2, we present here a spin symmetry analysis and ab-initio calculations, aiming to identify specific exchange-dominated physics that could offer insights into the current debate. We investigate two non-collinear coplanar magnetic orders reported in this compound: the helical and broken helical phases. Our symmetry analysis shows that magnetic-exchange alone results in the formation of an out-of-plane odd-wave order in momentum space with a single un-polarized nodal plane in both phases. Additionally, we identified an in-plane g-wave order that emerges exclusively in the broken helical phase, providing a distinguishing feature for this phase. Furthermore, we report a non-relativistic Edelstein effect with a distinct out-of-plane polarized spin density that dominates over spin-orbit coupling effects. Our ab-initio calculations reveal a significant contrast in the magnitude of this effect between both phases, which could serve as a means to identify the magnetic transition and distinguish them from other magnetic ground states proposed for this compound.

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 Néel vector formed by antiferroic dipole moments on an even number of crystal sublattices, underlining its distinction from collinear Néel 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° and 26° respectively, thus demonstrating the possibility of large altermagnetic responses without requiring the staggered Néel order of local dipole moments.

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↗

arXiv2024

Transport theory and spin-transfer physics in d-wave altermagnets

We develop a mesoscale transport theory for the charge and spin degrees of freedom of itinerant carriers in a $d$-wave altermagnet. Our effective Lagrangian description is built upon the slave-boson formulation of the microscopic $t-J$ model. We obtain a spin-polarized diffusive contribution to the effective Hamiltonian, with no counterpart in conventional antiferromagnetism and parametrized by the spin splitting, that is responsible for the so-called spin-splitter effect in $d$-wave altermagnets. We also elucidate the spin-transfer response of the itinerant fluid as well as the spin pumping into the altermagnet, which show previously unidentified combinations of the charge current and spatial partial derivatives (namely, {$j_{x}^{e}$,$\partial_{y}$} and {$j_{y}^{e}$,$\partial_{x}$}). The emergent spin-transfer physics in $d$-wave altermagnets opens up new possibilities for the dynamics of spin textures, such as the domain-wall motion driven by transverse charge currents. We also consider the effect of elastic distortions in the aforementioned transport properties.

cond-mat.mes-hall↗

arXiv2024

Highly Efficient Non-relativistic Edelstein effect in p-wave magnets

The origin and efficiency of charge-to-spin conversion, known as the Edelstein effect (EE), has been typically linked to spin-orbit coupling mechanisms, which require materials with heavy elements within a non-centrosymmetric environment. Here we demonstrate that the high efficiency of spin-charge conversion can be achieved even without spin-orbit coupling in the recently identified coplanar p-wave magnets. The non-relativistic Edelstein effect (NREE) in these magnets exhibits a distinct phenomenology compared to the relativistic EE, characterized by a strongly anisotropic response and an out-of-plane polarized spin density resulting from the spin symmetries. We illustrate the NREE through minimal tight-binding models, allowing a direct comparison to different systems. Through first-principles calculations, we further identify the p-wave candidate material CeNiAsO as a high-efficiency NREE material, revealing a 25 times larger response than the maximally achieved relativistic EE and other reported NREE in non-collinear magnetic systems with broken time-reversal symmetry. This highlights the potential for efficient spin-charge conversion in p-wave magnetic systems.

cond-mat.mes-hall↗

arXiv2024

Ultrafast electron dynamics in altermagnetic materials

Altermagnets constitute a new class of magnetic materials that combine properties previously thought to be exclusive to either antiferromagnets or ferromagnets, and have unique properties of their own. In particular, a combination of symmetries connecting magnetic sublattices gives rise to a band spin splitting exhibiting unconventional d, g, or i-wave character. Their unique electronic properties have already led to new spin-dependent transport effects. Here, we consider their spin and charge dynamics on ultrafast timescales. We use a minimal tight binding model that captures the main features of the altermagnetic candidate material KRu$_4$O$_8$. In the framework of this model, we compute the spin-dependent electronic scattering dynamics after ultrashort-pulse excitation and show through these microscopic calculations how electron-electron and electron-phonon scattering processes redistribute optically excited carriers in a 2D slice of the Brillouin zone. We find that the optically excited spin polarization is long lived (~1ps) compared to the electron-electron momentum scattering lifetime of roughly 10fs. This contrasts remarkably with the much shorter spin lifetimes observed in typical ultrafast electronic spin dynamics in conventional ferromagnets and antiferromagnets, making these pulse-driven spin excitation experiments a key probe of altermagnetism.

cond-mat.mtrl-sci↗

arXiv2024

P-wave magnets

The p-wave Cooper-pairing instability in superfluid $^{3}$He, characterized by a parity-breaking excitation gap, is regarded as one of the most rich and complex phenomena in physics. The possibility of a counterpart unconventional p-wave ordering of interacting fermions, in which a Fermi surface spontaneously breaks the parity symmetry, has been an open problem for many decades. Here we identify the realization of the counterpart of p-wave superfluidity in magnetism. We demonstrate a strong parity-breaking and anisotropic symmetry lowering of spin-polarized and time-reversal symmetric Fermi surfaces in a representative p-wave magnet CeNiAsO. As a direct experimental signature we predict a large spontaneous anisotropy of the resistivity. Abundant and robust realizations of the unconventional p-wave magnetism can be identified from suitable non-relativistic crystal-lattice and spin symmetries, without requiring strong correlations and extreme external conditions. This opens new prospects in fields ranging from topological phenomena to spintronics.

cond-mat.mes-hall↗

arXiv2024

Spontaneous Crystal Thermal Hall Effect in Insulating Altermagnets

We show that magnetic insulators with a collinear and compensated order can exhibit a thermal Hall effect even at zero magnetic field if they have altermagnetic symmetries. We predict a finite thermal Hall conductivity vector $\boldsymbolκ_\text{H}$ for a rutile-inspired effective spin model with Dzyaloshinskii-Moriya interaction. Within the linear spin-wave theory, we identify two magnon branches that carry identical Berry curvature and give rise to a finite $\boldsymbolκ_\text{H}$, which can be controlled by the Néel vector orientation and by strain. The thermal Hall response is further complemented with a spin Nernst response to contrast spin and heat transport in altermagnetic insulators with those in ferromagnets and antiferromagnets. Our results establish the crystal thermal Hall effect of magnons and we discuss material candidates for experimental realization, such as MnF$_2$, CoF$_2$, and NiF$_2$.

cond-mat.mes-hall↗

arXiv2023

Supercell Altermagnets

Altermagnets are compensated magnets with unconventional $d$, $g$, and $i$-wave spin order in reciprocal space. So far the search for new altermagnetic candidates has been focused on materials in which the magnetic unit cell is identical to the non-magnetic one, i.e. magnetic structures with zero propagation vector. Here, we substantially broaden the family of altermagnetic candidates by predicting supercell altermagnets. Their magnetic unit cell is constructed by enlarging the nonmagnetic primitive unit cell, resulting in a non-zero propagation vector for the magnetic structure. This connection of the magnetic configuration to the ordering of sublattices gives an extra degree of freedom to supercell altermagnets, which can allow for the control over the order parameter spatial orientation. We identify realistic candidates MnSe$_2$ with a $d$-wave order, and RbCoBr$_3$, CsCoCr$_3$, and BaMnO$_3$ with $g$-wave order. We demonstrate the reorientation of the order parameter in MnSe$_2$, which has two different magnetic configurations, whose energy difference is only 5 meV, opening the possibility of controlling the orientation of the altermagnetic order parameter by external perturbations.

cond-mat.mtrl-sci↗

arXiv2020

Theory of magnetism in the van der Waals magnet CrI3

We study the microscopical origin of anisotropic ferromagnetism in the van der Waals magnet CrI3. We conclude that the nearest neighbors exchange is well described by the Heisenberg-Kitaev-Gamma (HKGamma) model, and we also found a nonzero Dzyaloshinskii-Moriya interaction (DMI) on next nearest neighbors. Both Kitaev and DMI are known to generate a non-trivial topology of the magnons in the honeycomb lattice and have been used separately to describe the low energy regime of this material. We discuss that including one or the other leads to different signs of the Chern number. Furthermore, the topological gap at K-point seems to be mainly produced by DMI, despite it is one order of magnitude smaller than Kitaev. Finally, we show that by applying an external electric field perpendicular to the crystal plane, it is possible to induce DMI on nearest neighbors, and this could have consequences in non-collinear spin textures, such as domain walls and skyrmions.

cond-mat.mes-hall↗

arXiv2020

Topological magnonics in the two-dimensional van der Waals magnet CrI3

In this article, we calculate the magnon spectrum of Kitaev-Heisenberg magnets. This model has been recently proposed as a spin Hamiltonian to model $\text{CrI}_3$ and other two-dimensional magnets. It is a minimal spin Hamiltonian that includes a contribution stemming from a Heisenberg, isotropic exchange, and a contribution arising from a Kitaev interaction, anisotropic and frustrated exchange. Our calculations reveal the topological nature of the magnons and a gap that opens at the $K$ and $K^\prime$ points. These topological properties give rise to effects such as thermal Hall effect. In addition to the bulk properties, we calculate the magnon spectrum of nanoribbons illustrating the corresponding edge states.

cond-mat.mtrl-sci↗