As is well-known, the character of the π orbitals is of paramount importance for the chemical properties of the carbon allotropes and their derived compounds. While at equilibrium the nature of these orbitals is well understood, their photoinduced nonequilibrium behavior is under investigation. Here, we demonstrate that when a UV-laser pulse excites a carrier density larger than 10% of the π* density of state in graphite, a renormalization of the π-π* band gap takes place. This result has been achieved by detecting the transient reflectivity and the associated decay time of an infrared probe following the excitation of a UV pump pulse tuned across the π-π* absorption resonance. The pump photon energy at which both the transient reflectivity and the decay time are maximum is downshifted by 500 meV with respect to the relative absorption maximum at equilibrium. This finding is interpreted as a transient π-π* band gap shrinking of similar magnitude, near the M point of the Brillouin zone.

Pagliara, S., Galimberti, G., Mor, S., Montagnese, M., Ferrini, G., Grandi, M. S., Galinetto, P., Parmigiani, F., Photoinduced π- π* Band Gap Renormalization in Graphite, <<JOURNAL OF THE AMERICAN CHEMICAL SOCIETY>>, 2011; 133 (Aprile): 6318-6322. [doi:10.1021/ja1110738] [http://hdl.handle.net/10807/10623]

Photoinduced π- π* Band Gap Renormalization in Graphite

Pagliara, Stefania;Galimberti, Gianluca;Ferrini, Gabriele;
2011

Abstract

As is well-known, the character of the π orbitals is of paramount importance for the chemical properties of the carbon allotropes and their derived compounds. While at equilibrium the nature of these orbitals is well understood, their photoinduced nonequilibrium behavior is under investigation. Here, we demonstrate that when a UV-laser pulse excites a carrier density larger than 10% of the π* density of state in graphite, a renormalization of the π-π* band gap takes place. This result has been achieved by detecting the transient reflectivity and the associated decay time of an infrared probe following the excitation of a UV pump pulse tuned across the π-π* absorption resonance. The pump photon energy at which both the transient reflectivity and the decay time are maximum is downshifted by 500 meV with respect to the relative absorption maximum at equilibrium. This finding is interpreted as a transient π-π* band gap shrinking of similar magnitude, near the M point of the Brillouin zone.
Inglese
Pagliara, S., Galimberti, G., Mor, S., Montagnese, M., Ferrini, G., Grandi, M. S., Galinetto, P., Parmigiani, F., Photoinduced π- π* Band Gap Renormalization in Graphite, <<JOURNAL OF THE AMERICAN CHEMICAL SOCIETY>>, 2011; 133 (Aprile): 6318-6322. [doi:10.1021/ja1110738] [http://hdl.handle.net/10807/10623]
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10807/10623
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus ND
  • ???jsp.display-item.citation.isi??? 21
social impact