Academic Affiliation: Institute for Functional Matter and Quantum Technologies, University of Stuttgart, Germany

Talk: February 27, 2019

Ultrafast Charge-Density Wave Dynamics at the Atomic Scale

Combining the advantages of ultrafast laser spectroscopy and atomic-resolution scanning probe microscopy has been a dream for some time, which – owed to technological progress in reliable laser sources and picosecond electronics – has now become reality. I will discuss how focusing single-cycle Terahertz pulses into the junction of a scanning tunneling microscope enables spectroscopy of electron dynamics with atomic spatial and femtosecond temporal resolution.
We apply this new tool to study the dynamics of the charge-density wave (cdw) state in NbSe2 . We find that intense local THz excitation leads to a spatially heterogeneous response of the cdw at length scales down to 1 nm and relaxation times as fast as 600 fs. In particular, our local measurement reveals a low-energy excitation at 0.15 THz which we attribute to the previously hidden pinned phase mode excitation at individual atomic pinning sites. These measurements can be extended to a variety of low-dimensional correlated-electron materials and help us unravel the intricate connection between ultrafast dynamics and local fluctuations.