Spin-dependent photocurrent in topological insulator/magnetic insulator heterostructures*

The emerging field of 'topological spintronics' relies on interfacing the helical Dirac surface states of topological insulators (TIs) with magnetism. Heterostructures that combine TIs with insulating magnetic~materials are particularly relevant within this context. Here, we describe the discovery of a spin-dependent photocurrent~(PC) in heterostructures of~yttrium iron garnet (YIG) and 3D topological insulators. We find that the magnetic field-dependent PC maps out the magnetization state of the YIG layer, as confirmed~by a direct comparison with magneto-optical Kerr effect measurements. We gain insight into the phenomenon by studying the spin-dependent PC as a function of the chemical potential of the TI film, as well as by examining its variation with the temperature and the wavelength of the optical excitation.