Photoemission study of the filling-control metal-insulator transition in the two-dimensional system La_1.17-xPb_xVS_3.17

Using photoemission spectroscopy, the electronic structure around the two-dimensional filling-control metal-insulator transition (MIT) of La_1.17-xPb_x VS_3.17 has been studied. The density of state at the Fermi level disappears in going to the insulating phase, i.e., as x approaches ∼ 0.17 or as the temperature decreases at x = 0.15. The chemical potential shift with carrier doping shows a finite jump between the electron- and hole-doped samples and is unusually suppressed around x = 0.17. The results are contrary to a rigid band picture and show the presence of a pseudogap in the metallic phase.