Magnetic and Metal-Insulator Transitions through Bandwidth Control in Two-Dimensional Hubbard Models with Nearest and Next-Nearest Neighbor Transfers

Tsuyoshi Kashima; Masatoshi Imada

doi:10.1143/JPSJ.70.3052

paper

Magnetic and Metal-Insulator Transitions through Bandwidth Control in Two-Dimensional Hubbard Models with Nearest and Next-Nearest Neighbor Transfers

arXiv:cond-mat/0104348 · doi:10.1143/JPSJ.70.3052

Abstract

Numerical studies on Mott transitions caused by the control of the ratio between bandwidth and electron-electron interaction ( $U$ ) are reported. By using the recently proposed path-integral renormalization group(PIRG) algorithm, physical properties near the transitions in the ground state of two-dimensional half-filled models with the nearest and the next-nearest neighbor transfers ( $- t$ and $t^{'}$ , respectively) are studied as a prototype of geometrically frustrated system. The nature of the bandwidth-control transitions shows sharp contrast with that of the filling-control transitions: First, the metal-insulator and magnetic transitions are separated each other and the metal-insulator (MI) transition occurs at smaller $U$ , although the both transition interactions $U$ increase with increasing $t^{'}$ . Both transitions do not contradict the first-order transitions for smaller $t^{'} / t$ while the MI transitions become continuous type accompanied by emergence of {\it unusual metallic phase} near the transition for large $t^{'} / t$ . A nonmagnetic insulator phase is stabilized between MI and AF transitions. The region of the nonmagnetic insulator becomes wider with increasing $t^{'} / t$ . The phase diagram naturally connects two qualitatively different limits, namely the Hartree-Fock results at small $t^{'} / t$ and speculations in the strong coupling Heisenberg limit.

30 pages including 20 figures

Magnetic and Metal-Insulator Transitions through Bandwidth Control in Two-Dimensional Hubbard Models with Nearest and Next-Nearest Neighbor Transfers

Abstract

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