arXiv subjects

Thomas N. G. Meier

Publications and source records attributed to Thomas N. G. Meier.

6 recordsLinked to original sources

arXiv2026

Spin pumping reveals vortex-mediated angular-momentum dissipation at the superconducting transition

Spin pumping into superconductors is generally expected to become less efficient below the critical temperature $T_\textrm{c}$ because quasiparticle transport freezes out. Here we report a pronounced enhancement of the spin pumping-induced magnetic damping in Py/Nb heterostructures, confined to a narrow temperature interval immediately below the superconducting transition. The damping exceeds its normal-state value and therefore cannot be explained within the conventional quasiparticle picture of spin transport. The enhancement coincides with the finite-resistance vortex-creep regime of the Nb layers and disappears upon cooling into the pinned vortex state, indicating that mobile Abrikosov vortices provide an additional channel for spin-angular-momentum dissipation. These results establish ferromagnetic resonance as a sensitive probe of dissipative vortex dynamics in superconductors.

cond-mat.supr-con↗

arXiv2026

Electric-current control of anomalous Hall effect

We demonstrate robust and reversible electric-current control of the anomalous Hall effect (AHE) in a two-dimensional WTe2/Fe3GeTe2 (FGT) stack. Applying a current through Td-WTe2 leads to a giant modulation of the AHE of the adjacent FGT layer, with the relative change of the AHE conductivity exceeding 180%. Control experiments show that i) the observed effect is absent in pure FGT, ii) the modulation weakens in thicker FGT films, confirming its interfacial origin, and iii) the modulation peaks for bilayer WTe2, indicating that the Berry-curvature dipole (BCD) plays the dominant role in the modulation. We propose that the charge current I generates an out-of-plane magnetization Mz via BCD in WTe2 and Mz modifies the exchange splitting of FGT via the inverse magnetic proximity effect, thereby altering its Berry curvature and nontrivially influencing the AHE. The demonstrated method of AHE control offers new possibilities for magnetism control, i.e., for the study of AHE-transistors as well as electric-current control of quantum magnets, especially magnetic insulators.

cond-mat.mes-hall↗

arXiv2026

Magneto-Chiral Anisotropy in Josephson Diode Effect of All-Metallic Lateral Junctions with Interfacial Rashba Spin-Orbit Coupling

We explore the role of interfacial Rashba spin-orbit coupling (SOC) for the Josephson diode effect in all-metal diffusive Josephson junctions. Devices with Fe/Pt and Cu/Pt weak links between Nb leads reveal a Josephson diode effect in an in-plane magnetic field with magneto-chiral anisotropy according to the point symmetry of Rashba SOC. The Rashba SOC originates from inversion symmetry breaking at the metal-metal interfaces. A control sample with a plain Cu-layer as weak link, in contrast, exhibits an axis-symmetric diode effect. The Fraunhofer patterns display an apparent inverted hysteresis which can be traced back to stray fields resulting from the conventional hysteretic vortex pinning in the Nb contacts.

cond-mat.supr-con↗

arXiv2026

Current-tunable room temperature ferromagnetism and current-driven phase transitions

It is generally assumed that the application of a charge-current in ferromagnetic metals suppresses their ferromagnetic order through trivial Joule heating. Here, we demonstrate that a charge current can instead enhance magnetic ordering. Using a WTe2/Fe3Ge2Te (FGT) stack as a model system, we show that a charge current flowing in WTe2 controls the ferromagnetic properties and magnetic phase transition of the adjacent FGT via a current-induced effective magnetic-field arising from orbital magnetization. Remarkably, the charge current drives a substantial enhancement of the Curie temperature, boosting it well above room temperature. Furthermore, we show that the charge-current enables controlled tuning of the phase transitions in FGT, which confirms the scaling behaviour of a ferromagnet-paramagnet phase transition. This work provides a pathway for integrating two-dimensional ferromagnets into spintronic functionalities at technologically relevant temperatures and for exploring novel current-driven phenomena in ferromagnetic systems.

cond-mat.mtrl-sci↗

arXiv2026

Alloying Controlled Tuning of Interfacial Spin Orbit Interaction and Magnetic Damping in Crystalline FeCo Alloys

The discovery of intrinsic spin orbit fields in noncentrosymmetric ferromagnets has attracted considerable interest for both fundamental studies and technological applications. However, once such materials are synthesized, the strength of the spin orbit fields is difficult to tune because it is primarily a bulk property. Here, we demonstrate that the interfacial spin orbit interaction (SOI) in single crystalline FeCo thin films grown on GaAs(001) can be continuously tuned via alloying. Using spin orbit ferromagnetic resonance, we find that the Lande g factor, the Gilbert damping (alpha), and the interfacial spin orbit fields exhibit a common nonmonotonic dependence on Co concentration. A pronounced minimum occurs near x ~ 0.2 where an ultra low damping alpha ~ 0.0015 is achieved. Furthermore, we observe linear scaling between alpha and (g-2)^2, establishing a direct correlation between interfacial SOI and magnetic relaxation. These results identify alloying as an effective knob to engineer interfacial SOI and damping in single crystalline ferromagnet semiconductor heterostructures.

cond-mat.mtrl-sci↗

arXiv2022

Non-reciprocity of Vortex-limited Critical Current in Conventional Superconducting Micro-bridges

Non-reciprocity in the critical current has been observed in a variety of superconducting systems and has been called the superconducting diode effect. The origin underlying the effect depends on the symmetry breaking mechanisms at play. We investigate superconducting micro bridges of NbN and also NbN/magnetic insulator (MI) hybrids. We observe a large diode efficiency of $\approx$~30\% when an out-of-plane magnetic field as small as 25~mT is applied. In both NbN and NbN/MI hybrid, we find that the diode effect vanishes when the magnetic field is parallel to the sample plane. Our observations are consistent with the critical current being determined by the vortex surface barrier. Unequal barriers on the two edges of the superconductor strip result in the diode effect. Furthermore, the rectification is observed up to a temperature $\sim$10~K, which makes the device potential for diode based applications over larger temperature range than before.

cond-mat.supr-con↗