Ultrafast Electron Dynamics in Quasi-two-dimensional Quantum Materials

PC Department Seminar
Date: Sep 29, 2022
Time: 02:00 PM (Local Time Germany)
Speaker: Julian Maklar
FHI Department PC
Location: Building G
Room: Seminar Room 2.06
Host: Laurenz Rettig

Quantum materials are solids with tantalizing properties arising from special symmetry, dimensionality, topology, and many-body interactions between elementary degrees of freedom (charge, spin, orbital, and lattice). Gaining a microscopic understanding of quantum materials is critical as it implies the possibility of designing materials with desirable properties.

Ultrashort optical excitations offer a promising pathway to fulfill this goal, as they grant access to the relevant interactions on intrinsic timescales and facilitate control over novel light-enriched functionalities.
In this talk, I will discuss the ultrafast electron dynamics of several single-layer and layered quasi-2D quantum materials after photoexcitation. Using femtosecond time- and angle-resolved photoemission spectroscopy (trARPES), I demonstrate how the ultrafast response of broken-symmetry states upon light excitation allows uncovering the underlying energy landscape and microscopic interactions, with a focus on photoinduced charge-density-wave-to-metal transitions. Furthermore, I present the light-induced transition pathway to a long-lived metastable hidden state in the prototypical quantum material 1T-TaS2 and discuss how to achieve a high degree of control over the nonequilibrium phase transition using a sequence of optical pulses. The talk concludes with an outlook on future research of quantum materials enabled by a novel photoelectron detection scheme, momentum microscopy.