Local Symmetry Breaking and Spin Momentum Locking in Cuprates Superconductors

The 20th century has been dominated by the realization that symmetry and symmetry breaking are keys to much of the novel phenomena observed in physics today. Superconductivity for example requires both time-reversal and inversion symmetry, and the removal of one of these (e.g. time reversal through a magnetic field) leads to the suppression of the superconducting order. Recently however it has been realized that, even if the global symmetry of the system is retained, a local symmetry breaking can still induce a variety of novel fascinating behaviors.
In this talk I will present the effect of local breaking of inversion symmetry in cuprates superconductors and show that this leads to unusual phenomena and the appearance of a non-zero spin polarization with a well-defined spin momentum locking, that is strictly linked to the Fermi surface topology.
These results were enabled by the combination of UV laser with a state-of-the-art time of flight spectrometer combined with exchange scattering, allowing to perform spin and angle resolved photoemission spectroscopy experiments with unprecedented spin, time, energy and momentum resolution.