Related papers: Spin correlations near the surface of a three-dime…
Magnetic excitations and spin correlations near the interface of two spin-$\frac12$ Heisenberg antiferromagnets are considered using the spin-wave approximation. When the interaction between boundary spins differs essentially from exchange…
Using the spin-wave approximation elementary excitations of a semi-infinite two-dimensional $S=\frac12$ Heisenberg antiferromagnet are considered. The spectrum consists of bulk modes -- standing spin waves and a quasi-one-dimensional mode…
Recent numerical and analytical work has shown that for the square-lattice Heisenberg model the boundary can induce Dimer correlations near the edge which are absent in spin-wave theories and non-linear sigma model approaches. Here, we…
We analyze the dynamical nearest-neighbor and next-nearest-neighbor spin correlations in the 4-site and 8-site dynamical cluster approximation to the two-dimensional Hubbard model. Focusing on the robustness of these correlations at long…
With the commutation relations of the spin operators, we first write out the equations of motion of the spin susceptibility and related correlation functions that have a hierarchical structure, then under the "soft cut-off" approximation,…
We present a finite size spin wave calculation on the Heisenberg antiferromagnet on the triangular lattice focusing in particular on the low-energy part of the excitation spectrum. For s=1/2 the good agreement with the exact diagonalization…
We consider a special correlation function in the isotropic spin-$\half$ Heisenberg antiferromagnet. It is the probability of finding a ferromagnetic string of (adjacent) spins in the antiferromagnetic ground state. We give two different…
We consider the quantum ferromagnetic Heisenberg model in three dimensions, for all spins $S\geq 1/2$. We rigorously prove the validity of the spin-wave approximation for the excitation spectrum, at the level of the first non-trivial…
We use linked cluster series expansion methods to estimate the values of various short distance correlation functions in $S=1/2$ Heisenberg antiferromagnets at T=0, for dimension $d=1,2,3$. The method incorporates the possibility of…
We use quantum Monte Carlo simulations to study effects of free edges in the two-dimensional spin-1/2 Heisenberg antiferromagnet. We find that the magnetic response of an edge is smaller than the bulk susceptibility. This counter-intuitive…
We report a neutron scattering study of the instantaneous spin correlations in the two-dimensional spin S=5/2 square-lattice Heisenberg antiferromagnet Rb_2MnF_4. The measured correlation lengths are quantitatively described, with no…
We discuss spin-$\frac12$ two-dimensional (2D) Heisenberg antiferromagnet (AF) on a square lattice at T=0 in strong magnetic field H near its saturation value $H_c$. A perturbation approach is proposed to obtain spectrum of magnons with…
For a class of quasi-one-dimensional clusters, by using exact diagonalization, we study the effect of side spins on the spin-spin correlations on chain. Our calculations show that the side spins added in the same sublattice can effectively…
Results are presented for spin-wave dispersions in geometrically frustrated stacked triangular antiferromagnets with a thin film or semi-infinite geometry having either zero, easy-plane, or easy-axis anisotropy. Surface effects on the…
We report a neutron scattering study of the spin correlations for the spin 5/2, two-dimensional antiferromagnet Rb_2MnF_4 in an external magnetic field. Choosing fields near the system's bicritical point, we tune the effective anisotropy in…
We present a series expansion study of spin-S square-lattice Heisenberg antiferromagnets. The numerical data are in excellent agreement with recent neutron scattering measurements. Our key result is that the correlation length for S>1/2…
Investigation of dynamical excitations is difficult but crucial to the understanding of many exotic quantum phenomena discovered in quantum materials. This is particularly true for highly frustrated quantum antiferromagnets whose dynamical…
We present low-temperature dynamic properties of the quantum two-dimensional antiferromagnetic Heisenberg model with spin S=1/2. The calculation of the dynamic correlation function is performed by combining a projection operator formalism…
Spin correlations in an interacting electron liquid are studied in the high-frequency limit and in both two and three dimensions. The third-moment sum rule is evaluated and used to derive exact limiting forms (at both long- and…
The Heisenberg model for S=1/2 describes the interacting spins of electrons localized on lattice sites due to strong repulsion. It is the simplest strong-coupling model in condensed matter physics with wide-spread applications. Its…