We report the measurement of spin current induced charge accumulation, the inverse Edelstein effect (IEE), on the surface of a candidate topological Kondo insulator SmB6 single crystal. Robust surface conduction channel of SmB6 has been shown to exhi
bit large degree of spin-momentum locking, and spin polarized current through an external ferromagnetic contact induces the spin dependent charge accumulation on the surface of SmB6. The dependences of the IEE signal on the bias current, an external magnetic field direction and temperature are consistent with the anticlockwise spin texture for the surface band in SmB6 in the momentum space, and the direction and magnitude of the effect compared with the normal Edelstein signal are clearly explained by the Onsager reciprocal relation. Furthermore, we estimate spin-to-charge conversion efficiency, the IEE length, as 4.46 nm that is an order of magnitude larger than the efficiency found in other typical Rashba interfaces, implying that the Rashba contribution to the IEE signal could be small. Building upon existing reports on the surface charge and spin conduction nature on this material, our results provide additional evidence that the surface of SmB6 supports spin polarized conduction channel.
The Kondo insulator compound SmB6 has emerged as a strong candidate for the realization of a topologically nontrivial state in a strongly correlated system, a topological Kondo insulator, which can be a novel platform for investigating the interplay
between nontrivial topology and emergent correlation driven phenomena in solid state systems. Electronic transport measurements on this material, however, so far showed only the robust surface dominated charge conduction at low temperatures, lacking evidence of its connection to the topological nature by showing, for example, spin polarization due to spin momentum locking. Here, we find evidence for surface state spin polarization by electrical detection of a current induced spin chemical potential difference on the surface of a SmB6 single crystal. We clearly observe a surface dominated spin voltage, which is proportional to the projection of the spin polarization onto the contact magnetization, is determined by the direction and magnitude of the charge current and is strongly temperature dependent due to the crossover from surface to bulk conduction. We estimate the lower bound of the surface state net spin polarization as 15 percent based on the quantum transport model providing direct evidence that SmB6 supports metallic spin helical surface states.
we have fabricated transparent electronic devices based on graphene materials with thickness down to one single atomic layer by the transfer printing method. The resulting printed graphene devices retain high field effect mobility and have low contac
t resistance. The results show that the transfer printing method is capable of high-quality transfer of graphene materials from silicon dioxide substrates, and the method thus will have wide applications in manipulating and delivering graphene materials to desired substrate and device geometries. Since the method is purely additive, it exposes graphene (or other functional materials) to no chemical preparation or lithographic steps, providing greater experimental control over device environment for reproducibility and for studies of fundamental transport mechanisms. Finally, the transport properties of the graphene devices on the PET substrate demonstrate the non-universality of minimum conductivity and the incompleteness of the current transport theory.
