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Room temperature spin Hall effect in graphene/MoS <sub/>2</sub> van der Waals heterostructures
摘要： Graphene is an excellent material for long distance spin transport but allows little spin manipulation. Transition metal dichalcogenides imprint their strong spin-orbit coupling into graphene via proximity effect, and it has been predicted that efficient spin-to-charge conversion due to spin Hall and Rashba-Edelstein effects could be achieved. Here, by combining Hall probes with ferromagnetic electrodes, we unambiguously demonstrate experimentally spin Hall effect in graphene induced by MoS2 proximity and for varying temperature up to room temperature. The fact that spin transport and spin Hall effect occur in different parts of the same material gives rise to a hitherto unreported efficiency for the spin-to-charge voltage output. Remarkably for a single graphene/MoS2 heterostructure-based device, we evidence a superimposed spin-to-charge current conversion that can be indistinguishably associated with either the proximity-induced Rashba-Edelstein effect in graphene or the spin Hall effect in MoS2. By comparing our results to theoretical calculations, the latter scenario is found the most plausible one. Our findings pave the way towards the combination of spin information transport and spin-to-charge conversion in two-dimensional materials, opening exciting opportunities in a variety of future spintronic applications.
关键词： Spin Hall effect,Spin-orbit proximity,Rashba-Edelstein effect,Graphene,Transition metal dichalcogenides
更新于2025-09-23 15:22:29
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Nonlocal spin-charge conversion via Rashba spin-orbit interaction
摘要： We show theoretically that conversion between spin and charge by spin-orbit interaction in metals occurs even in a nonlocal setup where magnetization and spin-orbit interaction are spatially separated if electron diffusion is taken into account. Calculation is carried out for the Rashba spin-orbit interaction treating the coupling with a ferromagnet perturbatively. The results indicate the validity of the concept of effective spin gauge field (spin motive force) in the nonlocal configuration. The inverse Rashba-Edelstein effect observed for a trilayer of a ferromagnet, a normal metal and a heavy metal can be explained in terms of the nonlocal effective spin gauge field.
关键词： nonlocal setup,effective spin gauge field,spin-charge conversion,Rashba spin-orbit interaction,electron diffusion,inverse Rashba-Edelstein effect
更新于2025-09-19 17:15:36
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Tuning spin-charge interconversion with quantum confinement in ultrathin bismuth films
摘要： Spin-charge interconversion (SCI) phenomena have attracted a growing interest in the field of spintronics as a means to detect spin currents or manipulate the magnetization of ferromagnets. The key ingredients to exploit these assets are a large conversion efficiency, the scalability down to the nanometer scale, and the integrability with optoelectronic and spintronic devices. Here, we show that, when an ultrathin Bi film is epitaxially grown on a Ge(111) substrate, quantum size effects arising in nanometric Bi islands drastically boost the SCI efficiency, even at room temperature. Using x-ray diffraction, scanning tunneling microscopy, and spin- and angle-resolved photoemission, we obtain a clear picture of the film morphology, crystal, and electronic structures. We then directly probe SCI with three different techniques: magneto-optical Kerr effect to detect the charge-to-spin conversion generated by the Rashba-Edelstein effect (REE), optical spin orientation, and spin pumping to generate spin currents and measure the spin-to-charge conversion generated by the inverse Rashba-Edelstein effect (IREE). The three techniques show a sizable SCI only for 1–3-nm-thick Bi films corresponding to the presence of bismuth nanocrystals at the surface of germanium. Due to three-dimensional quantum confinement, those nanocrystals exhibit a highly resistive volume separating metallic surfaces where SCI takes place by (I)REE. As the film size increases, the Bi film becomes continuous and semimetallic leading to the cancellation of SCIs occurring at opposite surfaces, resulting in an average SCI that progressively decreases and disappears. These results pave the way for the exploitation of quantum size effects in spintronics.
关键词： Rashba-Edelstein effect,bismuth films,spintronics,quantum size effects,Spin-charge interconversion
更新于2025-09-10 09:29:36
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Current-driven magnetization switching in ferromagnetic bulk Rashba semiconductor (Ge,Mn)Te
摘要： Multiferroic materials with both ferroelectric and ferromagnetic orders provide a promising arena for the electrical manipulation of magnetization through the mutual correlation between those ferroic orders. Such a concept of multiferroics may expand to semiconductor with both broken symmetries of spatial inversion and time reversal, that is, polar ferromagnetic semiconductors. Here, we report the observation of current-driven magnetization switching in one such example, (Ge,Mn)Te thin films. The ferromagnetism caused by Mn doping opens an exchange gap in original massless Dirac band of the polar semiconductor GeTe with Rashba-type spin-split bands. The anomalous Hall conductivity is enhanced with increasing hole carrier density, indicating that the contribution of the Berry phase is maximized as the Fermi level approaches the exchange gap. By means of pulse-current injection, the electrical switching of the magnetization is observed in the (Ge,Mn)Te thin films as thick as 200 nm, pointing to the Rashba-Edelstein effect of bulk origin. The efficiency of this effect strongly depends on the Fermi-level position owing to the efficient spin accumulation at around the gap. The magnetic bulk Rashba system will be a promising platform for exploring the functional correlations among electric polarization, magnetization, and current.
关键词： anomalous Hall effect,ferromagnetic semiconductors,Rashba-Edelstein effect,magnetization switching,multiferroic materials
更新于2025-09-04 15:30:14