Spin dynamics and non-linear effects in Magnetic Topological Insulator – DYNTOP

TThis project will explore spin dynamics and ultra-fast processes in magnetic topological insulators. These very recent materials combine topological states and magnetic phases, making them compounds exhibiting remarkable properties: existence of quantum surface states; ferromagnetic phase; anormal quantum Hall effect; helical or chiral states. All this suggests various potentialities (spin current, spin-charge converter, THz source, quantum bit). In order to evaluate these materials, this consortium will explore their fundamental properties, such as the spin texture of surface states, the dynamics of spin states, relaxation mechanisms, non-linear effects and spin-charge transfer. To carry out the most complete study, the consortium will gather experienced and complementary teams, bringing together all the necessary skills and state of the art experiments. First, the synthesis of materials by molecular beam epitaxy will be carried out within the consortium (INSP), as well as in collaboration with a foreign partner strongly involved in this field. We will thus have access to a wide variety of magnetic topological insulators, ordered (e.g. MnSb2Te4) or disordered (e.g. CrxBi2-xTe3). Several approaches will be developed to control doping (irradiation, hydrogenation, gating) in order to manipulate the Fermi level in the vicinity of the Dirac point. Multiple experimental techniques will be implemented: photocurrent under polarized excitation, Faraday effect photoinduced ps / fs, spectroscopy and THz emission. Spectroscopy will make possible to follow the evolution of quantum states and to understand the band structure and the properties of spins, in particular topological states. Ultrafast spectroscopy will provide access to the dynamics and relaxation process of spins and carriers, as well as to the study of spin-charge conversion mechanisms.