2001/04/30 by Tsuyoshi Kashima, Masatoshi Imada
Physics and Astronomy · #cond-mat.str-el
paper · pdf · doi:10.1143/jpsj.70.3052
published as J. Phys. Soc. Jpn. 70 (2001) 3052 · 30 pages including 20 figures
arxiv created 2001/08/10 · arxiv updated 2009/11/30
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.