Tetsuo Ogawa — Page 2

arXiv2004

Instability toward biexciton crystallization in one-dimensional electron-hole systems

One-dimensional (1D) electron-hole (e-h) systems in a high-density regime is investigated by means of bozonization techniques. It turned out that the systems are insulating even at the high density limit and that the exciton Mott transition (insulator-to-metal transition) never occurs at absolute zero temperature. The insulating ground state exhibits a strong instability towards the crystallization of biexcitons.

cond-mat.str-el↗

arXiv2004

Phase diagram for the exciton Mott transition in infinite-dimensional electron-hole systems

To understand the essence of the exciton Mott transition in three-dimensional electron-hole systems, the metal-insulator transition is studied for a two-band Hubbard model in infinite dimensions with interactions of electron-electron (hole-hole) repulsion U and electron-hole attraction -U'. By using the dynamical mean-field theory, the phase diagram in the U-U' plane is obtained (which is exact in infinite dimensions) assuming that electron-hole pairs do not condense. When both electron and hole bands are half-filled, two types of insulating states appear: the Mott-Hubbard insulator for U > U' and the biexciton-like insulator for U < U'. Even when away from half-filling, we find the phase transition between the exciton- or biexciton-like insulator and a metallic state. This transition can be assigned to the exciton Mott transition, whereas the Mott-Hubbard transition is absent.

cond-mat.str-el↗