Stripe Phase in the t-J model

C. Stephen Hellberg, Efstratios Manousakis

Douglas J. Scalapino, Steven R. White

Cristian Kusko, R.S. Markiewicz

In stripe phases, a ``hidden order'' can exist as an order parameter on the charged stripes. A simple example arises in an unrestricted Hartree-Fock calculation of the Hubbard model, where a (metastable) solution is found which closely resembles the stripe phase of White and Scalapino. By comparison with uniform mean-field solutions, it is demonstrated that this phase develops from phase separation, and the order on the charged stripes is identified. The interface surface tension becomes negative for sufficiently narrow stripes, at which point the stripes begin to meander, gradually crossing from vertical to diagonal with decreasing doping.

R. Lemański, James K. Freericks, Grzegorz Banach

The observation of charge stripe order in the doped nickelate and cuprate materials has motivated much theoretical effort to understand the underlying mechanism of the stripe phase. Numerical studies of the Hubbard model show two possibilities: (i) stripe order arises from a tendency toward phase separation and its competition with the long-range Coulomb interaction or (ii) stripe order inherently arises as a compromise between itinerancy and magnetic interactions. Here we determine the restricted phase diagram of the two-dimensional Falicov-Kimball model and see that it displays rich behavior illustrating both possibilities in different regions.

Tôru Sakai, Didier Poilblanc

Steven R. White, Douglas J. Scalapino

We make a critical analysis of numerical results for and against phase separation and stripe formation in the $t\ensuremath{-}J$ model. We argue that the frustrated phase separation mechanism for stripe formation requires phase separation at too high a doping for it to be consistent with existing numerical studies of the $t\ensuremath{-}J$ model. We compare variational energies for various methods, and conclude that the most accurate calculations for large systems appear to be from the density-matrix renormalization group. These calculations imply that the ground state of the doped $t\ensuremath{-}J$ model is striped, not phase separated.