Ground State of the Many-Electron System

S. Fraga, Gulzari L. Malli, L. H. Thomas

R Sato

We construct the exact ground states of a class of models for correlated electronic systems in d dimensions. We introduce generalized models for heavy-fermion systems and those for bilayer systems. By the optimal ground state approach, we show that the models have superconducting ground states via the -pairing mechanism. We also obtain the criteria for the stability of charge-density-wave states.

Pang Xiao‐feng, Ping Li

Effects of the nonadiabatic phonon fluctuations on the ground state of coupled one-dimensional electron-phonon systems with high and low electron-densities were investigated by a new ansatz including correlated interaction of the displacement and squeezing. The correlated effect resulted in noticeable reduction of ground state energy of the systems, and obvious increases of binding energy of the polarons occurred. Thus, the stabilities of the polaron and of the systems were significantly enhanced, exactly steady ground state of the Holstein model, then, was obtained by the new ansatz for the coupled electron-phonon systems. In general, the new ansatz were found to be very relevant for the strong coupling and large squeezing cases in nonadiabatically coupled electron-photon systems.

L. C. M. Miranda, D. ter Haar

Д. В. Дмитриев, V. Ya. Krivnov, А. А. Овчинников

We have found the exact ground state for two electronic models on a linear chain. The first model describes a half-filling electron system at the ferromagnet-antiferromagnet transition point. In the singlet ground state the spin correlators show giant spiral magnetic ordering, with the period of a spiral equal to the system size. The second electronic model describes the point where the ground state has giant spiral off-diagonal long-range order and is, therefore, superconducting. We suggest the formation of a ground state with giant spiral order (ferromagnetic or off-diagonal) as a probable scenario of the subsequent destruction of the ferromagnetism and the superconductivity.