Collective modes of SDW in 1D extended Hubbard model at quarter-filling

Hanqin Ding, Jun Zhang

Yuh Tomio, Yoshikazu Suzumura

The collective modes representing density fluctuation in a spin density wave (SDW) have been examined for a one-dimensional electron system of a quarter-filled extended Hubbard model with the next-nearest-neighbor interaction ( V 2 ). Within the random phase approximation (RPA), we obtain a new collective mode, which appears with increasing V 2 . The mode describes the relative motion between density wave with up spin and that with down spin. The gap in the excitation spectrum vanishes at a critical value of V 2 corresponding to the onset of the coexistence of 2 k F -SDW, 2 k F -charge density wave and 4 k F -SDW in the ground state ( k F being the Fermi wave vector).

Satoshi Ejima, Satoshi Nishimoto

Norikazu Tomita, Hideo Fukutome

Frédéric Mila, X. Zotos

We used exact diagonalization of small clusters and exact results in various limits to determine the phase diagram and the critical exponents of the one-dimensional (1D) U-V model at quarter-filling. We found an instability of the Luttinger liquid to a charge density wave (CDW) insulator across a boundary going from ( U, V ) = (+ ∞ , 2 t ) to (4 t , + ∞ ). In the metallic phase, the dominant fluctuations are superconducting if V is large enough and spin density wave (SDW) otherwise. In the latter case, the critical exponent α of the momentum distribution does not exceed 9/16. The relevance of these results to 1D organic conductors is discussed.

Jian Zhong, Kaiyi Zhang, K. A. Chao +2 more