Chirality induced spin and orbital Edelstein response in nonmagnetic B20 bulk crystals: The role of geometry, spin-orbit coupling, and finite temperature Alberto Marmodoro, Ondřej Šipr, Ilja Turek, Annika Johansson, Sergiy Mankovsky, et al. Physical Review B, 2026 Chiral crystals have a noncentrosymmetric unit cell and can manifest spin-orbit coupling (SOC)-induced band splitting, even in the absence of an atomic magnetic moment. We examine the particular case of B20 compounds, with AlPt as representative material, by means of first-principles electronic structure calculations. We show how nonzero, but punctually compensated k textures for both the spin and the orbital magnetic moment, emerge as a function of the lattice geometry, SOC, and in dependence on finite temperature. An applied electric field perturbation is shown to set up a bulk Edelstein effect in terms of both spin and orbital magnetic moment.
Kramers nodal lines in intercalated TaS2 superconductors Yichen Zhang, Yuxiang Gao, Aki Pulkkinen, Xingyao Guo, Jianwei Huang, et al. Nature Communications, 2025 Kramers degeneracy is one fundamental embodiment of the quantum mechanical nature of particles with half-integer spin under time reversal symmetry. Under the chiral and noncentrosymmetric achiral crystalline symmetries, Kramers degeneracy emerges respectively as topological quasiparticles of Weyl fermions and Kramers nodal lines (KNLs), anchoring the Berry phase-related physics of electrons. However, an experimental demonstration for ideal KNLs well isolated at the Fermi level is lacking. Here, we establish a class of noncentrosymmetric achiral intercalated transition metal dichalcogenide superconductors with large Ising-type spin-orbit coupling, represented by In x TaS2, to host an ideal KNL phase. We provide evidence from angle-resolved photoemission spectroscopy with spin resolution, angle-dependent quantum oscillation measurements, and ab-initio calculations. Our work not only provides a realistic platform for realizing and tuning KNLs in layered materials, but also paves the way for exploring the interplay between KNLs and superconductivity, as well as applications pertaining to spintronics, valleytronics, and nonlinear transport.
Atomistic spin dynamics simulations of magnonic spin Seebeck and spin Nernst effects in altermagnets Markus Weißenhofer, Alberto Marmodoro Physical Review B, 2024 Magnon band structures in altermagnets are characterized by an energy splitting of modes with opposite chirality, even in the absence of applied external fields and relativistic effects, because of an anisotropy in the Heisenberg exchange interactions. We perform quantitative atomistic spin dynamics simulations based on electronic structure calculations on rutile RuO2, a prototypical “d-wave” altermagnet, to study magnon currents generated by thermal gradients. We report substantial spin Seebeck and spin Nernst effects, i.e., longitudinal or transverse spin currents, depending on the propagation direction of the magnons with respect to the crystal, together with a finite spin accumulation associated with nonlinearities in the temperature profile. Our findings are consistent with the altermagnetic spin-group symmetry, as well as predictions from linear spin-wave theory and semiclassical Boltzmann transport theory. Published by the American Physical Society 2024
Temperature Dependence of Relativistic Valence Band Splitting Induced by an Altermagnetic Phase Transition Mahdi Hajlaoui, Sunil Wilfred D'Souza, Libor Šmejkal, Dominik Kriegner, Gauthier Krizman, et al. Advanced Materials, 2024 Altermagnetic (AM) materials exhibit non‐relativistic, momentum‐dependent spin‐split states, ushering in new opportunities for spin electronic devices. While the characteristics of spin‐splitting are documented within the framework of the non‐relativistic spin group symmetry, there is limited exploration of the inclusion of relativistic symmetry and its impact on the emergence of a novel spin‐splitting in the band structure. This study delves into the intricate relativistic electronic structure of an AM material, α−MnTe. Employing temperature‐dependent angle‐resolved photoelectron spectroscopy across the AM phase transition, the emergence of a relativistic valence band splitting concurrent with the establishment of magnetic order is elucidated. This discovery is validated through disordered local moment calculations, modeling the influence of magnetic order on the electronic structure and confirming the magnetic origin of the observed splitting. The temperature‐dependent splitting is ascribed to the advent of relativistic spin‐splitting resulting from the strengthening of AM order in α−MnTe as the temperature decreases. This sheds light on a previously unexplored facet of this intriguing material.
Revisiting Electronic Topological Transitions in the Silver–Palladium (AgcPd1−c) Solid Solution: An Experimental and Theoretical Investigation Florian Reiter, Alberto Marmodoro, Andrei Ionut Mardare, Cezarina Cela Mardare, Achim Walter Hassel, et al. Materials, 2024 Multiple thick film samples of the AgcPd1−c solid solution were prepared using physical vapour deposition over a borosilicate glass substrate. This synthesis technique allows continuous variation in stoichiometry, while the distribution of silver or palladium atoms retains the arrangement into an on-average periodic lattice with smoothly varying unit cell parameters. The alloy concentration and geometry were measured over a set of sample points, respectively, via energy-dispersive X-ray spectroscopy and via X-ray diffraction. These results are compared with ab initio total energy and electronic structure calculations based on density functional theory, and using the coherent potential approximation for an effective medium description of disorder. The theoretically acquired lattice parameters appear in qualitative agreement with the measured trends. The numerical study of the Fermi surface also shows a variation in its topological features, which follow the change in silver concentration. These were related to the electrical resistivity of the AgcPd1−c alloy. The theoretically obtained variation exhibits a significant correlation with nonlinear changes in the resistivity as a function of composition. This combined experimental and theoretical study suggests the possibility of using resistivity measurements along concentration gradients as a way to gain some microscopic insight into the electronic structure of an alloy.
Chiral Magnons in Altermagnetic RuO2 Libor Šmejkal, Alberto Marmodoro, Kyo-Hoon Ahn, Rafael González-Hernández, Ilja Turek, et al. Physical Review Letters, 2023 Magnons in ferromagnets have one chirality, and typically are in the GHz range and have a quadratic dispersion near the zero wave vector. In contrast, magnons in antiferromagnets are commonly considered to have bands with both chiralities that are degenerate across the entire Brillouin zone, and to be in the THz range and to have a linear dispersion near the center of the Brillouin zone. Here we theoretically demonstrate a new class of magnons on a prototypical d-wave altermagnet RuO_{2} with the compensated antiparallel magnetic order in the ground state. Based on density-functional-theory calculations we observe that the THz-range magnon bands in RuO_{2} have an alternating chirality splitting, similar to the alternating spin splitting of the electronic bands, and a linear magnon dispersion near the zero wave vector. We also show that, overall, the Landau damping of this metallic altermagnet is suppressed due to the spin-split electronic structure, as compared to an artificial antiferromagnetic phase of the same RuO_{2} crystal with spin-degenerate electronic bands and chirality-degenerate magnon bands.
Chirality-inverted Dzyaloshinskii-Moriya interaction Khalil Zakeri, Alberto Marmodoro, Albrecht von Faber, Sergiy Mankovsky, Hubert Ebert Physical Review B, 2023 The Dzyaloshinskii-Moriya interaction (DMI) is an antisymmetric exchange interaction, which is responsible for the formation of topologically protected spin textures in chiral magnets. Here, by measuring the dispersion relation of the DM energy, we quantify the atomistic DMI in a model system, i.e., a Co double layer on Ir(001). We unambiguously demonstrate the presence of a chirality-inverted DMI, i.e., a sign change in the chirality index of DMI from negative to positive, when comparing the interaction between nearest neighbors to that between neighbors located at longer distances. The effect is in analogy to the change in the character of the Heisenberg exchange interaction from, e.g., ferromagnetic to antiferromagnetic. We show that the pattern of the atomistic DMI in epitaxial magnetic structures can be very complex and provide critical insights into the nature of DMI. We anticipate that the observed effect is general and occurs in many magnetic nanostructures grown on heavy-element metallic substrates.
High-Throughput Design of Magnetocaloric Materials for Energy Applications: MM´X alloys Nuno M. Fortunato, Andreas Taubel, Alberto Marmodoro, Lukas Pfeuffer, Ingo Ophale, et al. Advanced Science, 2023 Magnetic refrigeration offers an energy efficient and environmental friendly alternative to conventional vapor-cooling. However, its adoption depends on materials with tailored magnetic and structural properties. Here a high-throughput computational workflow for the design of magnetocaloric materials is introduced. Density functional theory calculations are used to screen potential candidates in the family of MM'X (M/M' = metal, X = main group element) compounds. Out of 274 stable compositions, 46 magnetic compounds are found to stabilize in both an austenite and martensite phase. Following the concept of Curie temperature window, nine compounds are identified as potential candidates with structural transitions, by evaluating and comparing the structural phase transition and magnetic ordering temperatures. Additionally, the use of doping to tailor magnetostructural coupling for both known and newly predicted MM'X compounds is predicted and isostructural substitution as a general approach to engineer magnetocaloric materials is suggested.
Temperature-induced changes in the magnetism of Laves phase rare-earth-iron intermetallics by ab initio calculations O. Šipr, S. Mankovsky, J. Vackář, H. Ebert, A. Marmodoro Physical Review B, 2022 Laves RFe 2 compounds, where R is a rare earth, exhibit technologically relevant properties associated with the interplay between their lattice geometry and magnetism. We apply ab initio calculations to explore how magnetic properties of Fe in RFe 2 systems vary with temperature. We found that the ratio between the orbital magnetic moment µ orb and the spin magnetic moment µ spin increases with increasing temperature for YFe 2 , GdFe 2 , TbFe 2 , DyFe 2 , and HoFe 2 . This increase is significant and it should be experimentally observable by means of x-ray magnetic circular dichroism. We conjecture that the predicted increase of the µ orb /µ spin ratio with temperature is linked to the reduction of hybridization between same-spin-channel states of atoms with fluctuating magnetic moments and to the associated increase of their atomic-like character.
Spin waves in disordered materials Paweł Buczek, Stefan Thomas, Alberto Marmodoro, Nadine Buczek, Xabier Zubizarreta, et al. Journal of Physics Condensed Matter, 2018
