First evidence of transient interactions between $��\to��^*$ optical excitations and image potential states in graphite

• DOI: 10.48550/arxiv.0910.4473
• Publication Date: 2009-01-01
• Authors: Montagnese, M.; Pagliara, S.; Conte, S. Dal; Galimberti, G.; Ferrini, G.; Parmigiani, F.
• Keywords: Materials Science (cond-mat.mtrl-sci); FOS: Physical sciences

Here we report the experimental evidence of the interactions between the excitations of the $��\to��^*$ optical transition and the image potential states (IPS) of highly oriented pyrolitic graphite (HOPG). By using non-linear angle resolved photoelectron spectroscopy (NL-ARPES) we show that the IPS photoemission intensity, the effective mass, and the linewidth exhibit a strong variation when the photon energy is tuned across the $��\to��^*$ saddle points in the 3.1 - 4.5 eV photon energy range. A model based on the self-energy formalism is proposed to correlate the effective mass and the linewidth variations to transient many body effects, when a high carriers density (in the $10^{20}$ cm$^{-3}$ range) is created by the absorption of a coherent light pulse. This finding brings a clear evidence of a high IPS-bulk coupling in graphite and opens the way for exploiting the IPS as a sensitive, nonperturbing probe for the many-body dynamics in materials.<br/>5 pages, 3 figures; FIG1 and FIG2 modified, added references, corrected typos<br/>