Talk 1:
Nonequilibrium DMFT Inspired by Experiments on 1T-TaS2
Martin Eckstein, University of Hamburg
Time-resolved experiments on the layered material 1T-TaS2 have been a major motivation for the development of nonequilibrium dynamical mean-field theory (DMFT). In this talk, I will review how DMFT has been used to interpret the dynamics in this unconventional charge-density-wave Mott system, starting from the investigation of photo-doping and the subsequent decay of doublons, to the formation and dynamics of photo-induced midgap states and the excitation of coherent amplitude modes. I will this use the example to highlight the current status of nonequilibrium DMFT simulations, along with open challenges (long-time simulations and accurate real-time impurity solvers). If time permits, I will also briefly review a possible interpretation of recent experiments which show how the metal-insulator of 1T-TaS2 can be affected by placing the material in a cavity.
Talk 2:
Ultrafast Electronic Structure Engineering in 1T-TaS2: Role of Doping and Amplitude Mode Dynamics
Uwe Bovensiepen, University of Duisburg-Essen
In strongly correlated transition metal dichalcogenides, an intricate interplay of polaronic distortions, stacking arrangement, and electronic correlations determines the nature of the insulating state. The response of the electronic structure to optical excitations reveals the effect of chemical electron doping on this complex interplay. Transient changes in pristine and electron-doped 1T-TaS2 are measured by femtosecond time-resolved photoelectron spectroscopy and compared to theoretical modeling based on non-equilibrium dynamical mean-field theory and density functional theory. Real-time oscillatory spectral changes induced by the charge density wave amplitude mode are consistent with modulations of the electron-electron interactions and electron hoppings. Our analysis furthermore indicates doping-induced changes in the stacking and an enhanced fraction of monolayers. Our work demonstrates how the combination of time-resolved spectroscopy and advanced theoretical modeling provides insights into the physics of correlated transition metal dichalcogenides.