Terahertz spectroscopy of collective charge density wave dynamics at the atomic scale

Charge density waves (CDWs) are wave-like electron density modulations exhibiting collective amplitude and phase dynamics. Atomic impurities induce spatial heterogeneity in the charge-ordered phase. This research uses terahertz pump-probe spectroscopy in a scanning tunneling microscope (STM) to achieve atomic-scale resolution of ultrafast CDW dynamics in 2H-NbSe₂. Tip-enhanced terahertz pulses excite CDW oscillations varying in magnitude and frequency near atomic impurities. The spatially structured response arises from overlapping phase excitations from randomly distributed defects. This method allows studying correlated material dynamics at the intrinsic length scale of their interactions.

Shaoxiang Sheng, Mohamad Abdo, Steffen Rolf-Pissarczyk, Kurt Lichtenberg, Susanne Baumann, Jacob A. J. Burgess, Luigi Malavolti, Sebastian Loth