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We demonstrate electrical detection of spin currents in metallic nanostructures. In a conductor with nonzero spin-orbit coupling, a spin current is predicted in a direction perpendicular to the applied electric field, giving rise to a spin Hall effect, where electrons with opposite spin orientations accumulate at opposite edges of the sample. Conversely, when a spin current is present, a charge imbalance is expected, following the Onsager reciprocal relations between spin and charge currents. We report direct electronic measurements of this effect in a lateral geometry by using a ferromagnetic electrode in combination with a tunnel barrier to inject a spin-polarized current in a paramagnetic conductor. We observe a laterally induced voltage in the latter that results from the conversion of the injected spin current into charge imbalance owing to the spin-orbit coupling. Such a voltage is proportional to the component of the injected spins that is perpendicular to the plane defined by the spin-current direction and the voltage probes. By using this technique in CoFe–Al2O3–Al devices, we determine the spin Hall conductivity of aluminum. [ABSTRACT FROM AUTHOR]

We demonstrate a large enhancement of the spin accumulation in monolayer graphene following electron-beam induced deposition of an amorphous carbon layer at the ferromagnet-graphene interface. The enhancement is 104-fold when graphene is deposited onto poly(methyl metacrylate) (PMMA) and exposed with sufficient electron-beam dose to cross-link the PMMA, and 103-fold when graphene is deposited directly onto SiO2 and exposed with identical dose. We attribute the difference to a more efficient carbon deposition in the former case due to an increase in the presence of compounds containing carbon, which are released by the PMMA. The amorphous carbon interface can sustain very large current densities without degrading, which leads to very large spin accumulations exceeding 500 μeV at room temperature. [ABSTRACT FROM AUTHOR]

We report on electric-field and temperature-dependent transport measurements in exfoliated thin crystals of the Bi2Se3 topological insulator. At low temperatures (<50 K) and when the chemical potential lies inside the bulk gap, the crystal resistivity is strongly temperature dependent, reflecting inelastic scattering due to the thermal activation of optical phonons. A linear increase of the current with voltage is obtained up to a threshold value at which current saturation takes place. We show that the activated behavior, the voltage threshold, and the saturation current can all be quantitatively explained by considering a single optical-phonon mode with energy ℏΩ≈ meV. This phonon mode strongly interacts with the surface states of the material and represents the dominant source of scattering at the surface at high electric fields. [ABSTRACT FROM AUTHOR]