Who: Cheol-Hwan Park (Seoul National University)
Place: CFM seminar room
Date: Wednesday, 30 August 2017, 12:00
After the discovery by Zhang et al. [Nature Phys. 10, 387-393 (2014)] of hidden spin polarizations in non-magnetic, centrosymmetric materials, the scope of spintronics has been broadened to systems with PT symmetry. In the first part of the talk, I will discuss the orbital version of this physics, the hidden orbital polarization . Hidden orbital polarization is much more abundant in nature than the spin counterpart since no spin-orbit coupling is required and is responsible for the generation of hidden spin polarization via spin-orbit coupling. We look into materials like diamond, silicon and transition metal dichalcogenides.
In the second part of the talk, I will discuss the chiral anomaly in Weyl semimetals, an imbalance in the charge carriers with opposite chiralities . Through our first-principles calculations, we show that a sizable energy gap may open up at the intersection of the zeroth Landau levels originating from opposite-chirality Weyl points. These zeroth Landau levels have so far believed to remain gapless in Weyl semimetals.
 Ji Hoon Ryoo and Cheol-Hwan Park, "Hidden orbital polarization in diamond, silicon, germanium, gallium arsenide and layered materials", NPG Asia Materials 9, e382 (2017).
 Pilkwang Kim, Ji Hoon Ryoo and Cheol-Hwan Park, "Chiral anomaly in Weyl semimetals is not robust", arXiv:1707.01103.