科研之友
微信
新浪微博
Facebook
分享链接
摘要
The effect of doping in the two-dimensional Hubbard model is studied within finite-temperature exact diagonalization combined with cluster dynamical mean-field theory. By employing a mixed basis involving cluster sites and bath molecular orbitals for the projection of the lattice Green's function onto 2 x 2 clusters, a considerably more accurate description of the low-frequency properties of the self-energy is achieved than in a pure site picture. To evaluate the phase diagram, the transition from Fermi-liquid to non-Fermi-liquid behavior for decreasing hole doping is studied as a function of Coulomb energy, next-nearest-neighbor hopping, and temperature. The self-energy component Sigma(X) associated with X=(pi, 0) is shown to develop a collective mode above E-F, whose energy and strength exhibits a distinct dispersion with doping. This low-energy excitation gives rise to non-Fermi-liquid behavior as the hole doping decreases below a critical value delta(c), and to an increasing particle-hole asymmetry, in agreement with recent photoemission data. This behavior is consistent with the removal of spectral weight from electron states above EF and the opening of a pseudogap, which increases with decreasing doping. The phase diagram reveals that delta(c) approximate to 0.15... 0.20 for various system parameters. For electron doping, the collective mode of Sigma(X)(omega) and the concomitant pseudogap are located below the Fermi energy, which is consistent with the removal of spectral weight from the hole states just below E-F. The critical doping, which marks the onset of non-Fermi-liquid behavior, is systematically smaller than for hole doping.
- 出版日期2009-10
- 单位中国人民大学
