2009/10/20 by Hunpyo Lee, Yu-Zhong Zhang, Harald O. Jeschke +2 · 1 citation
Physics and Astronomy · #cond-mat.str-el
paper · pdf · doi:10.1103/physrevlett.104.026402
published as Phys. Rev. Lett. 104, 026402 (2010) · 5 pages and 5 figures
We investigate the properties of a two-orbital Hubbard model with unequal bandwidths on the square lattice in the framework of the dynamical cluster approximation (DCA) combined with a continuous-time quantum Monte Carlo (CT QMC) algorithm. We explore the effect of short-range spatial fluctuations on the nature of the metal-insulator transition and the possible occurrence of an orbital-selective Mott transition (OSMT), as a function of cluster size Nc. We observe that for Nc=2 no OSMT is present, instead a band insulator state for both orbitals is stabilized at low temperatures due to the appearance of an artificial local ordered state. For Nc=4 the DCA calculations suggest the presence of five different phases which originate out of the cooperation and competition between spatial fluctuations and orbitals of different bandwidths and a OSMT phase is stabilized. Based on our results, we discuss the nature of the gap opening.