Optical Materials Design of Transition-Metal Dichalcogenides and Frustrated Mott Insulators
MPSD Seminar
- Datum: 07.10.2016
- Uhrzeit: 11:00 - 12:00
- Vortragende(r): Martin Claassen
- Department of Applied Physics, Stanford University, California
- Ort: CFEL (Bldg. 99)
- Raum: Seminar Room I, EG.076
- Gastgeber: Angel Rubio

Here, we discuss a two-pronged approach to manipulate the topology of a
band insulator, as well as topological order in a Mott insulator. We
first consider monolayer transition-metal dichalcogenides (TMDCs), and
show that their low-energy description as massive 2D relativistic
fermions fails to hold for optical pumping. Instead, the added
complexity of a realistic materials description leads to a novel
mechanism to optically induce topologically-protected chiral edge modes,
facilitating optically-switchable conduction channels that are
insensitive to disorder. We develop a strategy to understand
non-equilibrium Floquet-Bloch bands and topological transitions directly
from ab initio calculations, and illustrate for the example of WS2 that
control of chiral edge modes can be dictated solely from symmetry
principles and is not qualitatively sensitive to microscopic materials
details. Second, we extend these ideas to strongly-correlated systems
and show that pumping frustrated Mott insulators with
circularly-polarized light can drive the effective spin system across a
phase transition to a chiral spin liquid (CSL). We find that the
transient time evolution of a Kagome lattice Hubbard model is
well-captured by an effective spin description, where circular
polarization promotes a staggered scalar spin chirality Si · (Sj × Sk)
directly to the Hamiltonian level. We fingerprint the ensuing phase
diagram and find a stable photo-induced CSL in proximity to the
equilibrium ground state. The results presented suggest new avenues to
marry dynamical symmetry breaking, strong interactions, and ab initio
materials modelling, to access elusive phase transitions that are not
readily accessible in equilibrium.