Phonon-mode-specific modulation of electronic states in molybdenum dioxide

Near-infrared pump and extreme ultraviolet probe transient absorption spectroscopy is employed to unravel the phonon-mode-specific modifications of electronic states near the Fermi energy in molybdenum dioxide. We observe distinct fingerprints of two coherent phonon modes at a frequency of 6 and <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mn>11</a:mn><a:mspace width="0.28em"/><a:mtext>THz</a:mtext></a:mrow></a:math> which differ vastly in their energy-dependent modulations of the electronic response. By combining our measurements with density functional theory calculations, we show that the measured energy-dependent contrast between the phonon modes is primarily governed by the modification of the projected density of states. These findings highlight the pivotal role of lattice dynamics in the ultrafast electronic response.