Nonlinear detection of spin currents in graphene with non-magnetic electrodes

The abilities to inject and detect spin carriers are fundamentalfor research on transport and manipulation of spininformation1,2. Pure electronic spin currents have been recentlystudied in nanoscale electronic devices using a non-local lateralgeometry, both in metallic systems3 and in semiconductors4.To unlock the full potential of spintronics we must understandthe interactions of spin with other degrees of freedom. Suchinteractions have been explored recently, for example, by usingspin Hall5???7 or spin thermoelectric effects6,8,9. Here we presentthe detection of non-local spin signals using non-magneticdetectors, through an as-yet-unexplored nonlinear interactionbetween spin and charge. In analogy to the Seebeck effect10,where a heat current generates a charge potential, wedemonstrate that a spin current in a paramagnet leads to acharge potential, if the conductivity is energy dependent. Weuse graphene11 as a model system to study this effect, asrecently proposed12. The physical concept demonstrated hereis generally valid, opening newpossibilities for spintronics.