Electron dynamics in low dimensions: a time- and momentum-resolved view

Isabella Gierz

Tuesday May 24th, at 10.00

1525-323 

Abstract:

When reducing the dimensionality of a material electronic correlations become more and more important with dramatic effects on the electronic properties. Our goal is to engineer the electronic properties of various low-dimensional material systems with light, complementing the more traditional routes of electronic structure control using chemistry, pressure, or magnetic fields. Using the analogy with the Kapitza pendulum, I will show that driven systems are distinct from matter at equilibrium because the interaction with a periodic driving field results in the formation of new effective Hamiltonians with new eigenstates. Famous examples for electronic structure control by periodic driving include light-induced superconductivity in cuprates [1] and K3C60 [2] using resonant excitation of the crystal lattice, as well as the formation of photon-dressed Floquet-Bloch states inducing a topological phase transition in Bi2Se3 [3].

I will present our time- and angle-resolved photoemission results on epitaxial monolayer and bilayer graphene for various driving regimes including interband excitation, free carrier absorption, and resonant phonon excitation.

[1] W. Hu et al., Nature Materials 13, 705 (2014)
[2] M. Mitrano et al., Nature 530, 461 (2016)
[3] Y. H. Wang et al. Science 342, 453 (2013)