Enhanced low-temperature entropy and flat-band ferromagnetism in the t-J model on the sawtooth lattice

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

卷:310

Article; Proceedings Paper

Honecker, A. ; Richter, J.

关键词: flat band;    localized states;    frustrated lattice;    t-J model;    entropy;   

DOI  :  10.1016/j.jmmm.2006.10.357

来源: Elsevier

【 摘 要 】

Using the example of the sawtooth chain, we argue that the t-J model shares important features with the Hubbard model on highly frustrated lattices. The lowest single-fermion band is completely flat (for a specific choice of the hopping parameters t(ij) in the case of the sawtooth chain), giving rise to single-particle excitations which can be localized in real space. These localized excitations do not interact for sufficient spatial separations such that exact many-electron states can also be constructed. Furthermore, all these excitations acquire zero energy for a suitable choice of the chemical potential mu. This leads to: (i) a jump in the particle density at zero temperature, (ii) a finite zero-temperature entropy, (iii) a ferromagnetic ground state with a charge gap when the flat band is fully occupied and (iv) unusually large temperature variations when mu is varied adiabatically at finite temperature. (c) 2006 Elsevier B.V. All rights reserved.

【 授权许可】

Free