Temperature-induced plasmons in a graphite sheet

The low-frequency electronic excitations of a two-dimensional graphite sheet are studied within A zero-gap graphite sheet only exhibits the interband e-h excitations at zero temperature. Electrons and holes grow rapidly as temperature increases from zero. Temperature induces the intraband excitations and thus the intraband plasmons. A graphite sheet is predicted to be the first undoped system which could exhibit the low-frequency plasmons purely due to temperature. Whether such plasmons exist are mainly determined by temperature and momentum. The temperature-induced plasmons in a graphite sheet are identified as the 2D plasmons from the momentum dependence of plasmon frequencies. They quite differ from the optical plasmons in the three-dimensional graphite or graphite intercalation compounds. The inelastic light scattering spectroscopies could be used to verify the temperature-induced plasmons.