arXiv subjects

Qinwu Gao

Publications and source records attributed to Qinwu Gao.

4 recordsLinked to original sources

arXiv2026

Vortex-mediated spin current injection into two-dimensional superconductor NbSe2

Injection of pure spin current into superconductors remains a major challenge in superconducting spintronics. Previous studies have primarily focused on spin-polarized quasiparticles and spin-triplet supercurrents, while vortices, ubiquitous topological defects in type-2 superconductors, have been theoretically proposed as alternative carriers of spin angular momentum, yet direct experimental evidence is still lacking. Here, we report the vortex-mediated spin current injection in NbSe2/LiAl2Fe3O8(LAFO) bilayer, an Ising superconductor/ferrimagnetic insulator heterostructure. Under an out-of-plane temperature gradient and an in-plane magnetic field, the NbSe2/LAFO bilayer shows a pronounced thermoelectric peak near the upper critical magnetic field, which has the opposite sign to the conventional vortex Nernst signal observed in a single-layer NbSe2. The sign reversal suggests that the vortex flow induced by spin current injection is opposite to the flow driven by the temperature gradient, which is consistent with theoretical mechanisms including spin-vorticity transmutation and the inverse vortex spin Hall effect. By mapping the field temperature phase diagram, we reveal that the spin current injection occurs exclusively in the vortex liquid phase of NbSe2. Absence of the thermoelectric signal above the superconducting transition temperature further rules out the quasiparticle contribution. Our results establish vortices as efficient carriers of spin information in superconductors, opening a new route towards vortex-mediated superconducting spintronic devices.

cond-mat.supr-con↗

arXiv2026

Observation of Dyakonov-Perel-type magnon spin relaxation in uniaxial antiferromagnetic insulators

Long-distance transport of magnon spin currents in antiferromagnetic (AFM) insulators has attracted tremendous attention recently, however, the AFM magnon spin relaxation mechanisms remain elusive. Here, we report that the Dyakonov-Perel-type magnon spin relaxation mechanism governs the spin current transport along the easy axis in two prototypical uniaxial AFM insulators, Cr2O3 and alpha-Fe2O3. First, an over 450% enhancement of the first-harmonic nonlocal signal induced by a magnetic field is observed prior to the spin-flop transition, which can be well-interpreted by our model incorporating Dyakonov-Perel-type magnon spin relaxation. Secondly, we find that the magnon spin diffusion length in both crystals increases with magnetic field and saturates at fields above 0.8 T, consistent with our model. Finally, the temperature dependence of the zero-field magnon spin diffusion length in both AFM insulators can be qualitatively explained through our model. These findings are valuable for the development of low-dissipation antiferromagnetic spintronic devices.

cond-mat.mes-hall↗

arXiv2026

Epitaxial Growth and Anomalous Hall Effect in High-Quality Altermagnetic $α$-MnTe Thin Films

The recent identification of $α$-MnTe as a candidate altermagnet has attracted considerable interest, particularly for its potential application in magnetic random-access memory. However, the development of high-quality thin films - essential for practical implementation - has remained limited. Here, we report the epitaxial growth of centimeter-scale $α$-MnTe thin films on InP(111) substrates via molecular beam epitaxy (MBE). Through X-ray diffraction (XRD) analysis, we construct a MnTe phase diagram that provides clear guidance for stabilizing the pure $α$-MnTe phase, revealing that it is favored under high Te/Mn flux ratios and elevated growth temperatures. Cross-sectional electron microscopy confirms an atomically sharp film-substrate interface, consistent with a layer-by-layer epitaxial growth mode. Remarkably, these high-quality $α$-MnTe films exhibit a pronounced anomalous Hall effect (AHE) originating from Berry curvature, despite a net magnetic moment approaching zero - a signature of robust altermagnetic character. Our work establishes a viable route for synthesizing wafer-scale $α$-MnTe thin films and highlights their promise for altermagnet-based spintronics and magnetic sensing.

cond-mat.mtrl-sci↗

arXiv2025

Anisotropic Field Suppression of Morin Transition Temperature in Epitaxially Grown Hematite Thin Films

We have demonstrated the existence of the Morin transition in epitaxially grown hematite thin films exceeding a critical thickness. The Morin transition temperature can be suppressed by magnetic fields applied both parallel and perpendicular to the Dzyaloshinskii-Moriya (DM) vector, exhibiting a distinct anisotropic behavior that is consistent with bulk hematite crystals. Detailed analysis explains the anisotropic behavior and provides a method for determining the DM strength, which remains nearly constant across the sample thickness over four orders of magnitude. Our findings obtained with transport measurements offer a valuable approach for studying antiferromagnetic spin configurations in thin films and nanodevices.

cond-mat.mtrl-sci↗