Using coherent potential approximation we study zero-temperature Mott transition of the half-filled Hubbard model in a two-dimensional square lattice with geometrical frustration. It turns out that the geometrical frustration reduces the gap between the Hubbard bands. As a result the metallic phase is stabilized up to a fairly large value of the on-site Coulomb interaction. We found that the critical value UC for the Mott transition is enhanced by the geometrical frustration. Our results are in good agreement with the ones obtained by the single-site dynamical mean-field theory. | Communications in Physics, Vol. 23, No. 1 (2013), pp. 49-55 MOTT TRANSITION OF THE HALF-FILLED HUBBARD MODEL IN A TWO-DIMENSIONAL FRUSTRATED LATTICE LE DUC ANH Department of Physics, Hanoi National University of Education HOANG ANH TUAN Institute of Physics, VAST Abstract. Using coherent potential approximation we study zero-temperature Mott transition of the half-filled Hubbard model in a two-dimensional square lattice with geometrical frustration. It turns out that the geometrical frustration reduces the gap between the Hubbard bands. As a result the metallic phase is stabilized up to a fairly large value of the on-site Coulomb interaction. We found that the critical value UC for the Mott transition is enhanced by the geometrical frustration. Our results are in good agreement with the ones obtained by the single-site dynamical mean-field theory. I. INTRODUCTION Strongly correlated electron system with geometrical frustration exhibits a variety of phenomena and is presently a major topic of great interest in the condensed-matter community[1, 2]. The competition between strong electronic correlations and the geometrical frustration in metallic spinel compounds may cause some novel phenomena such as heavy fermion state in LiV2 O4 [3], superconductivity with relatively high transition temperature of TC = in LiT i2 O4 [4], and so forth. New aspects of the Mott metal-insulator transitions are also uncovered by the geometrical frustration, which is now one of the central issues in the physics of strongly correlated electron systems[5]. Among all possible microscopic models, the one-band Hubbard model is often used for a study of the interplay between the geometrical frustration and strong electronic correlations. Previous studies of such model on triangular and Kagom´e lattices have been performed by various approaches such as the fluctuation exchange approximation[6], quantum Monte Carlo calculations[7], coherent potential approximation[8], and cellular .
