Finite temperature effects in a one-dimensional Mott-Hubbard insulator: Angle-resolved photoemission study of Na0.96V2O5

We have made an angle-resolved photoemission study of a one-dimensional Mot t-Hubbard insulator Na0.96V2O5 and found that the spectra of the V 3d lower Hubbard band are strongly dependent on the temperature. We have calculated the one-particle spectral function of the one-dimensional t-J model at fin ite temperatures by exact diagonalization and compared them with the experi mental results. Good overall agreement is obtained between experiment and t heory. The strong finite temperature effects are discussed in terms of the existence of the "Fermi surface" of the spinon band.