Hidden spin and orbital polarizations

• Speaker: Prof. Park, Cheol-Hwan (Seoul National Univ)
• Date: October 10, 2017
• Place: Science Building 433

It has been widely accepted that in a crystal with time-reversal and inversion symmetry the electronic band is always double degenerate. Recently, it was found that even in centrosymmetric, non-magnetic materials, a Bloch state can have a local spin polarization, so-called hidden spin polarization. This discovery has significantly broadened the scope of spintronics. We find that the hidden orbital polarization (the orbital version of hidden polarization) is much more abundant in nature than the hidden spin polarization and it induces the hidden spin polarization if there is enough spin-orbit coupling. In this colloquium, I will briefly explain the spin-orbit coupling in solids, hidden spin polarization and hidden orbital polarization.

1. X. Zhang et al., “Hidden spin polarization in inversion-symmetric bulk crystals,” Nat. Phys. 10, 387 (2014).
   
2. J. H. Ryoo and C.-H. Park, “Hidden orbital polarization in diamond, Si, Ge, GaAs and layered materials,” NPG Asia Materials 9, e382 (2017).