In the last decade the quest for engineering new materials for spintronics and quantum computing applications lead to the discovery of a new class of systems with a remarkably strong spin-orbit coupling. Examples range from the celebrated iridium oxides to oxides interfaces and surfaces and polar semiconductors.In these materials spin-orbit coupling can be made comparable or larger than all other relevant energy scales, thereby reaching a regime where not only spin-dependent phenomena but all the properties of the system are strongly affected by spin-orbit interaction.
Focusing on the case of Rashba spin-orbit coupling (RSOC), in the present work we discuss various aspects of the physics of strong spin-orbit coupled materials.
We start by reviewing the unconventional transport properties of Rashba electron gases, showing how, in these systems, Drude’s paradigm breaks down and diffusive charge transport becomes strongly sensitive to the spin-orbit coupling strength.
We then turn our attention to correlated systems and, in particular, to the metal-insulator transition in the Hubbard model with spin-orbit interaction. After some general considerations on the effects of different kinds of spin-orbit coupling, we discuss the “phase diagram” of small Hubbard clusters with Rashba spin-orbit coupling (RSOC). We show that the peculiar way in which RSOC breaks the spin-rotational symmetry slows down and it changes the nature of the Mott transition exploiting the competition between two states having different symmetries and giving rise to a Pauli metallic ground-state.