Related papers: Superconducting Spiral Phase in the two-dimensiona…
We study spin fluctuation (SF) mediated superconductivity (SC) in a half-filled square lattice Hubbard model with the transfer matrices -t between nearest neighbor sites and -t' between a half of next nearest neighbor sites neighboring…
We carry out the variational Monte Carlo calculation to examine spatially inhomogeneous states in hole- and electron-doped cuprates. By using Gutzwiller approximation, we consider the excitations, arising from charge density, spin density…
In high-Tc cuprate superconductors, violation of time-reversal symmetry (${\cal T}$) has been observed experimentally. In order to explain this phenomenon, we consider a flux phase in the t-J model. The flux phase has a free energy higher…
Numerical and analytical studies of several models of correlated electrons are discussed. Based on exact diagonalization and variational Monte Carlo techniques, we have found strong indications that the two dimensional t-J model…
The minimal theory of spin of gapless quasiparticles coupled to fluctuating vortex defects in the phase of the d-wave superconducting order parameter at T=0 is studied. With the proliferation of the vortex loops the theory reduces to the…
Using the method which retains the rotation symmetry of spin components in the paramagnetic state and has no preset magnetic ordering, spectral and magnetic properties of the two-dimensional t-J model in the normal state are investigated…
We investigate the ground-state properties of a correlated model for the double-chain structure in cuprates. We consider the $t$-$J$ model, in which the nearest-neighbor spin interaction $J_1$ is smaller than the next-nearest-neighbor…
We explain qualitatively why the staggered flux state plays a central role in the SU(2) formulation of the t-J model, which we use to model the pseudogap state in underdoped cuprates. This point of view is supported by studies of projected…
We have studied the ground state properties of Hubbard model on long six-leg square cylinders with doped hole concentration per site $5.55\% \leq \delta\leq 12.5\%$ using density-matrix renormalization group. By keeping a large number of…
Hole doping into a correlated antiferromagnet leads to topological stripe correlations, involving charge stripes that separate antiferromagnetic spin stripes of opposite phase. Topological spin stripe order causes the spin degrees of…
We propose a model of a spatially modulated collective charge state of superconducting cuprates. The regions of higher carrier density (stripes) are described in terms of Luttinger liquids and the regions of lower density as a…
Influence of a spiral spin structure on the superconducting (SC) pairing in the most probable active $\gamma$ band of $Sr_2RuO_4$ is studied in the mean field approximation. Such structure with "incommensurate" vector $Q=2\pi(1/3,1/3)$ has…
An effective Hamiltonian for the Kohn-Luttinger superconductor is constructed and solved in the BCS approximation. The method is applied to the t-t' Hubbard model in two dimensions with the following results: (i) The superconducting phase…
We apply density functional theory band structure calculations, the coupled-cluster method, and exact diagonalization to investigate the microscopic magnetic model of the spin-1/2 compound Cu2GeO4. The model is quasi-two-dimensional, with…
Using computational techniques, it is shown that pairing is a robust property of hole doped antiferromagnetic (AF) insulators. In one dimension (1D) and for two-leg ladder systems, a BCS-like variational wave function with long-bond…
We report a large-scale density-matrix renormalization group study of the lightly doped Hubbard model on 4-leg cylinders at hole doping concentration $\delta=12.5\%$. By keeping a large number of states for long system sizes, we are able to…
The Shastry-Sutherland model is a two-dimensional frustrated spin model whose ground state is a spin gap state. We study this model doped with one and two holes on a 32-site lattice using exact diagonalization. When t'>0, we find that the…
We propose a new class of ground states for doped Mott insulators in the electron second-quantization representation. They are obtained from a bosonic resonating valence bond (RVB) theory of the t-J model. At half filling, the ground state…
We study the one-dimensional t-J-J'-model in the limit of small hole doping $x$ and small $J/t$, $J'/t$. Special emphasis is put on the regime $J'/J \approx .5$ where a spin gap is present at small doping and the undoped spin chain is…
Extensive numerical studies have demonstrated that the two-dimensional single-band Hubbard model contains much of the key physics in cuprate high-temperature superconductors. However, there is no definitive proof that the Hubbard model…