Related papers: The spin-1/2 square-lattice J_1-J_2 model: The spi…
We study the zero-temperature phase diagram of the $J_{1}^{XXZ}$--$J_{2}^{XXZ}$ Heisenberg model for spin-1 particles on an infinite square lattice interacting via nearest-neighbour ($J_1 \equiv 1$) and next-nearest-neighbour ($J_2 > 0$)…
Motivated by recent experiments on an S=1/2 antiferromagnet on the kagome lattice, we investigate the Heisenberg J1-J2 model with ferromagnetic J1 and antiferromagnetic J2. Classically the ground state displays Neel long range order with 12…
We provide strong evidence of the spin-nematic state in a paradigmatic ferro-antiferromagnetic $J_1$--$J_2$ model using analytical and density-matrix renormalization group methods. In zero field, the attraction of spin-flip pairs leads to a…
We have performed a numerical investigation of the ground state properties of the frustrated quantum Heisenberg antiferromagnet on the square lattice (``$J_1-J_2$ model''), using exact diagonalization of finite clusters with 16, 20, 32, and…
We investigate the quantum spin-1/2 zigzag chain with frustrated $J_1$-$J_2$ Heisenberg interactions, incorporating additional off-diagonal exchange interactions known as the $\Gamma$ term, both with and without an applied magnetic field.…
We study the ground state properties of the spin-1/2 frustrated ferromagnetic J1-J2 Heisenberg model on the square lattice, employing projected BCS wavefunctions with spin-triplet pairings of the spinon fields as trial wavefunctions. Based…
In this paper we reexamine the problem of the separation of spin and charge degrees of freedom in two dimensional strongly correlated systems. We establish a set of sufficient conditions for the occurence of spin and charge separation.…
We study the S=1/2 Heisenberg antiferromagnet on the pyrochlore lattice in the limit of strong easy-axis exchange anisotropy. We find, using only standard techniques of degenerate perturbation theory, that the model has a U(1) gauge…
With strong geometric frustration and quantum fluctuations, S=1/2 quantum Heisenberg antiferromagnets on the Kagome lattice has long been considered as an ideal platform to realize spin liquid (SL), a novel phase with no symmetry breaking…
We present a detailed numerical study of spin and charge dynamics of the two-dimensional Kondo lattice model with hopping t and exchange J. At T=0 and J > 0, the competition between the RKKY interaction and Kondo effect triggers a quantum…
The nature of the ground state of the spin $S=1/2$ Heisenberg antiferromagnet on the kagome lattice with breathing anisotropy (i.e., with different superexchange couplings $J_{\vartriangle}$ and $J_{\triangledown}$ within elementary up- and…
The zero-temperature phase diagram of the spin-$\frac{1}{2}$ $J_{1}$--$J_{2}$--$J_{1}^{\perp}$ model on an $AA$-stacked square-lattice bilayer is studied using the coupled cluster method implemented to very high orders. Both…
The spin-Peierls transition is modeled in the dimer phase of the spin-$1/2$ chain with exchanges $J_1$, $J_2 = \alpha J_1$ between first and second neighbors. The degenerate ground state generates an energy cusp that qualitatively changes…
We study the magnetic phase diagram of spin-3/2 fermions in a spatially anisotropic square optical lattice at quarter filling (corresponding to one particle per lattice site). In the limit of the large on-site repulsion the system can be…
The coupled cluster method (CCM) is used to study the zero-temperature properties of a frustrated spin-half ($s={1}{2}$) $J_{1}$--$J_{2}$ Heisenberg antiferromagnet (HAF) on a 2D chevron-square lattice. Each site on an underlying square…
Motivated by recent experiments on the frustrated quantum magnetic compound YbMgGaO4, we study an effective spin model on triangular lattice taking into account the effects of the spin-orbit coupling. We determine the classical ground-state…
Quantum spin liquids have been at the forefront of correlated electron research ever since their original proposal in 1973, and the realization that they belong to the broader class of intrinsic topological orders, along with the fractional…
We use the coupled cluster method to study the zero-temperature quantum phase diagram of the spin-$\frac{1}{2}$ $J_{1}$--$J_{2}$--$J_{1}^{\perp}$ model on the honeycomb bilayer lattice. In each layer we include both nearest-neighbor and…
The spin-$1/2$ Heisenberg antiferromagnet on the two-dimensional ruby and maple-leaf lattices is emerging as a new paradigmatic model of frustrated quantum magnetism, with the potential to realize intricate many-body phases on both mineral…
In this paper we analyze the groundstate and finite-temperature properties of a frustrated Heisenberg $J_1-J_2$ model on a honeycomb lattice by employing the Schwinger boson technique. The phase diagram and spin gap as functions of…