Gabriel Topp

Ultrafast topological quantum material engineering

Ultrafast material science offers the prospect of tailored material engineering below intrinsic thermalization time scales. In this talk, two experimentally relevant approaches for the ultrafast manipulation of topological properties via pulsed laser light are presented.

In the first approach, intense laser light is employed to control the effective electronic interactions in pyrochlore iridates. Combining time-dependent ab initio calculations and magnetic model simulations we show that an ultrafast laser modification of the local Hubbard U can transiently induce a topologically nontrivial Weyl phase that can be probed by time- and angle-resolved photoemission spectroscopy [1].

In the second approach, the topology of intermediate-angel twisted bilayer graphene is investigated by the Berry curvature of the weakly-interacting Bloch-electrons in an effective single-quasiparticle picture. It is shown that circularly polarized light can induce a tuneable transition to a topologically nontrivial Floquet band structure with a Berry curvature analogous to a Chern insulator [2]. Finally,  ongoing theoretical and experimental explorations of a light-induced anomalous Hall effect [3] in twisted bilayer graphene are discussed.

[1] Topp et al., Nat. Commun. 9 (1), 1-9 , 4452 (2018)
[2] Topp et al., Phys. Rev. Res. 1 (2), 023031  (2019)
[3] McIver et al., Nat. Phys., 16, 38–41 (2020)