Electronic motion up close
Charge density waves are wave-like patterns in a material’s electron density that can behave collectively. Shaoxiang Sheng et al. show a direct real-space observation of these collective dynamics at the atomic scale in the transition metal dichalcogenide 2H-NbSe2. Their technique utilizes a terahertz pulse that is enhanced at the tip of a scanning tunnelling microscope to excite oscillations of the charge density wave that vary in magnitude and frequency on the scale of individual atomic impurities. Measuring the current through the tip reveals overlapping phase excitations originating from randomly distributed atomic defects in the surface and creates a spatially structured response of the charge density wave.
See Shaoxiang Sheng et al.
Image: Kurt Lichtenberg, University of Stuttgart. Cover design: Laoise Mac Gabhann