Finite temperature effects in a one-dimensional mott-hubbard insulator: Angle-resolved photoemission study of Na_0.96V₂O₅

We have made an angle-resolved photoemission study of a one-dimensional Mott-Hubbard insulator Na_0.96V₂O₅ 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 finite temperatures by exact diagonalization and compared them with the experimental results. Good overall agreement is obtained between experiment and theory. The strong finite temperature effects are discussed in terms of the existence of the “Fermi surface” of the spinon band.