Interaction and Topological Effects in Quasi-2D Systems: Magnetism and Novel Optical Selection Rules

Föreläsning med Chalmers jubileumsprofessor Steven G Louie, Physics Department, University of California at Berkeley ochLawrence Berkeley National Lab, Berkeley, California

Abstract
Interaction and topological effects, as well as environmental screening, often dominate many of the quantum properties of reduced-dimensional systems and nanostructures. I will present two phenomena recently discovered in atomically thin two-dimensional materials.  First, we show that nontrivial band topology can dramatically change the photophysics of two-dimensional (2D) semiconductors. The optical strength and nature (i.e., helicity) of the photo-excited excitonic states are dictated by the optical matrix element winding number, a unique and heretofore unrecognized topological invariant which leads to new selection rules.  Second, together with experimental collaborators, we find that intrinsic long-range ferromagnetic order exists in pristine Cr2Ge2Te6 atomic layers. The behaviors of these quasi-2D insulating magnets are elucidated using a renormalized spin wave theory. Another remarkable finding from the latter study is that the magnetic transition temperature in these systems may be dramatically altered and controlled via a small applied magnetic field, which is expected to be a hallmark of 2D ferromagnetic crystals.

Professor Steven G. Louie kommer att vara på Chalmers 11-20 september.
Kontakta Mikael Fogelström om du vill träffa honom. 

Läs reportaget om jubileumsprofessor Steven G. Louie


​Kaffe serveras klockan 15.00 utanför Kollektorn.
Kategori Föreläsning
Plats: Kollektorn, lecture room, MC2-huset, MC2
Tid: 2017-09-14 15:15
Sluttid: 2017-09-14 16:00

Publicerad: on 06 sep 2017. Ändrad: ti 12 sep 2017