ALBA Synchrotron
Dr. Paolo Sessi - University of Wuerzburg – Institute of Physic - Bavaria, Germany
In a non-relativistic theory of solids, the spin degree of freedom appears just as an additional quantum number introduced to account for the Pauli exclusion principle. However, once the relativistic spin-orbit interaction is considered, spin moment and orbital motion become intimately coupled.
In recent years, condensed matter systems characterized by strong spin-orbit coupling have gain a lot of attention. This is due to the large variety of unconventional physical effects they host which, beyond their fundamental interest, represent a promising playground to develop new applications, being spintronics and magneto-electrics the most prominent examples. Since the key consequences of strong-spin orbit coupling usually manifest at boundaries, i.e. edges in 2D and surfaces in 3D, scanning probe techniques are ideal tools to visualize them with both high spatial and energy resolution.
In my talk, I will present recent results obtained in our group onto two prototypical systems: (i) Rashba surfaces: where the strong spin-orbit interaction causes a spin splitting of a spin-degenerate electron gas in the presence of a structure inversion asymmetric potential and (ii) topological insulators, where spin-orbit coupling acts as a kind of ’built-in magnetic field’ of a non-magnetic solid, that plays a role similar to the external magnetic field in the quantum Hall effect. In both cases I will describe experiments that through quantum interference allow not only to visualize the presence of unconventional edge states, but also to demonstrate their unusual properties. Finally, I will discuss more recent efforts focused to their controlled manipulation, which can be achieved by directly coupling them to well defined charge and magnetic external perturbations.