03.10.2023 New Joint Publication in Frustrated Magnetism

A joint publication with Jairo Sinova and Ricardo Zarzuela about spin-transfer and topological Hall effects in itinerant frustrated magnets has been published in Physical Review B.

They examine the spin-transfer and topological Hall physics of metallic frustrated magnets and show that SO(3) solitons and magnetic disclinations mediate previously unidentified contributions to the corresponding effects, with no analog in collinear magnetism. In particular, they present a minimal low-energy long-wavelength theory of the Yang-Mills type for the itinerant carriers and also discuss the emergent electrodynamics mediated by the topological solitons/defects arising in the noncoplanar magnetic background. They also considered the effect of symmetry reduction (with respect to the case of full rotational symmetry) on both spin-transfer and topological Hall responses of the magnetic conductor. Furthermore, they discuss experimental setups for the detection of the aforesaid Hall currents. Their findings open new avenues for the detection of topological solitons/defects in magnetic systems with order-parameter manifolds beyond the conventional S2 paradigm.

You can find the publication under Phys. Rev. B 108, 134402 (2023).

02.10.2023 New Joint Publication in Altermagnetism

A joint publication with Jairo Sinova and Libor Šmejkal about the saturation of the anomalous Hall effect at high magnetic fields in altermagnetic RuO2 has been published in APL Materials.

They used a field-induced reorientation of the Néel vector from the easy-axis toward the [110] hard-axis to demonstrate the anomalous Hall signal in this RuO2. They confirm the existence of an anomalous Hall effect in our RuO2 thin-film samples, whose set of magnetic and magneto-transport characteristics is consistent with the earlier report. By performing their measurements at extreme magnetic fields up to 68 T, they reach saturation of the anomalous Hall signal at a field Hc ≃ 55 T that was inaccessible in earlier studies but is consistent with the expected Néel-vector reorientation field.

You can find the publication under APL Mater. 11, 101103 (2023).

27.09.2023 New Publication in Antiferromagnetic Spintronics

A publication with Helen Gomonay about nonlinear magnon dynamics in Mn2Au has been published in Nature Communications.

They excite Mn2Au thin films with phase-locked single-cycle terahertz electromagnetic pulses and monitor the spin response with femtosecond magneto-optic probes. They observe signals whose symmetry, dynamics, terahertz-field scaling and dependence on sample structure are fully consistent with a uniform in-plane antiferromagnetic magnon driven by field-like terahertz NSOTs with a torkance of (150 ± 50) cm2 A−1 s−1. Their research indicates that fully coherent Néel-vector switching by 90° within 1 ps is within close reach.

You can find the publication under Nat Commun 14, 6038 (2023).

24.07.2023 New Joint Publication in Antiferromagnetic Spintronics

A joint publication with Tobias Wagner and Helen Gomonay about coupling of ferromagnetic and antiferromagnetic spin dynamics in Mn2Au/NiFe thin film bilayers has been published in Physical Review Letters.

They investigate magnetization dynamics of Mn2Au/Py (Ni80Fe20) thin film bilayers using broadband ferromagnetic resonance (FMR) and Brillouin light scattering spectroscopy. Their model reveals the dependence of the hybrid modes on the AFMR frequencies and interfacial coupling as well as the evanescent character of the spin waves that extend across the Mn2Au/Py interface.

You can find the publication under Phys.Rev.Lett.131,046701.

23.07.2023 Upcoming SPICE Workshop on Hybrid Correlated States and Dynamics in Quantum Materials

The SPICE workshop "Hybrid Correlated States and Dynamics in Quantum Materials" will be held from May 14th to 16th, 2024 at the historic WASEM winery, Ingelheim.

The workshop focusses on correlated states of electrons, that give rise to quantum matter, such as ordered magnets, spin liquids, superconductors, and topological materials. The exciting phenomena hosted and technological applications promised by these states of matter have further inspired the scientific community to engineer hybrids where different ingredients for correlations are provided by separate materials coupled together. Thus, such low-dimensional hybrid nanostructures have enabled engineering novel states of matter with intriguing physics, often not admitted by any single platform.

With the recent developments, theoretical and experimental, time reversal symmetry breaking via magnetism has emerged as a powerful tool to engineer novel unconventional superconducting states and phenomena such as nonreciprocity. At the same time, engineering of the superconducting condensate to bear a net spin employing magnet/superconductor hybrids has been demonstrated. This has opened prospects for superconducting spintronics devices enabling dissipationless spin torques and logic. Further, spin fluctuations appear to play a fundamental role in a large fraction of unconventional and two-dimensional superconductors including the recently discovered states in moiré materials. Therefore, these three seemingly disjoint fields are intricately relying on knowledge from each other and can best be tackled with an overview of all three. Providing this overview and a common discussion platform is the main goal of this workshop.

The workshop shall bring together experts and young researchers from three different communities: (i) Magnetism and Spintronics, (ii) Superconductivity and Strongly Correlated Electrons, and (iii) Low-dimensional nanostructures. The purview includes coherent and incoherent magnetization dynamics in conjunction with the various spintronics effects that allow its manipulation and detection. A key topic will be the recently discovered nonreciprocal effects in magnets e.g., chiral magnons, as well as superconductors, e.g., the superconducting diode effect. Recent discoveries regarding two-dimensional materials, multi-orbital superconductivity, Ising superconductors, topological superconductivity and quantum sensors coupled to magnets will also be central to the workshop portfolio. Employing fluctuations of currents (e.g, flow of spin or vortices) to probe the quantum nature of transport will form an exciting topic of discussion across communities. Finally, the case of spin fluctuations mediated superconductivity, that is believed to underlie a wide range of unconventional superconductors can best be discussed with the three communities present at the workshop.

05.07.2023 New Joint Publication in Antiferromagnetic Spintronics

A joint publication with Olena Gomonay about photocurrents, the Inverse faraday effect, and photospin Hall effect in Mn2Au has been published in APL Materials.

They reveal the emergence of large photocurrents of spin in collinear Mn2Au, whose properties can be understood as a result of a non-linear optical version of the spin Hall effect, which they refer to as the photospin Hall effect, encoded into the relation between the driving charge and resulting spin photocurrents. Moreover, they suggest that even a very small canting in Mn2Au can give rise to colossal spin photocurrents that are chiral in flavor. They conclude that the combination of staggered magnetization with the structural and electronic properties of this material results in a unique blend of prominent
photocurrents, which makes Mn2Au a unique platform for advanced optospintronics applications.

You can find the publication under APL Mater 11, 071106.

01.07.2023 Upcoming SPICE Workshop on Terahertz Spintronics: toward Terahertz Spin-based Devices

The SPICE workshop "Terahertz Spintronics: toward Terahertz Spin-based Devices" will be held from October 10th to 12th, 2023 at the historic WASEM winery, Ingelheim.

The workshop focusses on THz spintronics, which is a novel research field that combines magnetism and spintronic with ultrafast optics. Although ultrafast demagnetization of ferromagnetic materials at picosecond timescale has been first observed already three decades ago, recent years have seen the rapid development of THz spintronic devices stemming from ground breaking studies. In the last years, the numerous improvements made in material research (such as on topological insulators and antiferromagnetic materials), interface quality and device engineering have been central to both explore spin-based physics at THz frequencies and investigate to new concepts of spin based THz devices. These cover the full THz block chain (broad and narrowband THz generation and detection, together with control of radiation properties such as polarization and ellipticity) as well as new approaches for THz imaging and encoding THz information. This workshop will bring together world-leading scientists from a broad range of communities, generating further collaborations and developmentsin this emerging field.

You can apply online for the workshop until August 14th, 2023.

03.05.2023 New Joint Publication on Antiferromagnetic Spintronics

A joint publication with Libor Šmejkal about the electronic structure of the electrically switchable antiferromagnet CuMnAs has been published in npj Quantum Materials.

They report direct measurements of the electronic structure of single-crystalline thin films of tetragonal CuMnAs using angle-resolved photoemission spectroscopy (ARPES), including Fermi surfaces (FS) and energy-wavevector dispersions. This work underscores the need to control the chemical potential in tetragonal CuMnAs to enable the exploration and exploitation of the Dirac fermions with tunable masses, which are predicted to be above the chemical potential in the present samples.

You can find the publication under npj Quantum Materials volume 8, Article number: 19 (2023).

03.05.2023 New Joint Publication in Antiferromagnetic Spintronics

A joint publication with Jairo Sinova and Helen Gomonay about magnon eigenmode and polarization control in the easy-plane phase of hematite has been published in Physical Review B.

They describe how magnon eigenmodes in easy-plane antiferromagnetic insulators are linearly polarized and are not expected to carry any net spin angular momentum. Motivated by recent nonlocal spin transport experiments in the easy-plane phase of hematite, they perform a series of micromagnetic simulations in a nonlocal geometry at finite temperatures. They show that by tuning an external magnetic field, they can control the magnon eigenmodes and the polarization of the spin transport signal in these systems. They argue that a coherent beating oscillation between two orthogonal linearly polarized magnon eigenmodes is the mechanism responsible for finite spin transport in easy-plane antiferromagnetic insulators. The sign of the detected spin signal is also naturally explained by the proposed coherent beating mechanism. Their finding opens a path for on-demand control of the spin signal in a large class of easy-plane antiferromagnetic insulators.

You can find the publication under Phys. Rev. B 107, 184404 (2023).