Related papers: Low-dimensional Heisenberg magnets: Riemann zeta f…
We evaluate numerically certain multiple integrals representing nearest and next-nearest neighbor correlation functions of the spin-1/2 $XXZ$ Heisenberg infinite chain at finite temperatures.
Ordering of the classical Heisenberg antiferromagnet on the triangular lattice is studied by means of a mean-field calculation, a scaling argument and a Monte Carlo simulation, with special attention to its vortex degree of freedom. The…
We discuss spin-$\frac12$ Heisenberg antiferromagnet on simple square lattice in magnetic field $H$ using recently proposed bond-operator technique. It is well known that magnetically ordered phases of quantum magnets are well described at…
We use the density-matrix renormalization group technique developed by White \cite{white} to calculate the spin correlation functions $<{S}_{n+l}^z{S}_n^z>=(-1)^l \omega(l,N)$ for isotropic Heisenberg rings up to $N=70$ sites. The…
In this paper we present an extensive study of the thermodynamic properties of the two-dimensional quantum Heisenberg antiferromagnet on the square lattice; the problem is tackled by the pure-quantum self-consistent harmonic approximation,…
The ordering of weakly coupled random antiferromagnetic $S=1/2$ chains, as relevant for recent experimentally investigated spin chain materials, is considered theoretically. The one-dimensional isotropic Heisenberg model with random…
The square lattice spin-1/2 antiferromagnet containing a dilute concentration, $\delta$, of randomly placed ferromagnetic nearest-neighbor bonds is studied at low-temperature via non-linear $\sigma$-model techniques and by exact…
We present a spin-rotation-invariant Green-function theory of long- and short-range order in the ferro- and antiferromagnetic Heisenberg model with arbitrary spin quantum number S on a stacked square lattice. The thermodynamic quantities…
Measurements of the spin-lattice relaxation rate 1/T_1 by nuclear magnetic resonance for the one-dimensional Heisenberg antiferromagnet Sr_2CuO_3 have provided evidence for a diffusion-like contribution at finite temperature and small…
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…
A spin-wave theory of short-range order in the square lattice Heisenberg antiferromagnet is formulated. With growing temperature from T=0 a gapless mode is shown to arise simultaneously with opening a gap in the conventional spin-wave mode.…
The problem of weak ferromagnetism in antiferromagnets due to canting of magnetic moments was treated using Green's function technique. At first the eigenvalues and eigenfunctions of the electronic Hamiltonian corresponding to collinear…
Effective range is a quantity to characterize the energy dependence in two-body scattering strength, and is widely used in cold atomic systems especially across narrow resonances. Here we show that the effective range can significantly…
In low-dimensional magnets, thermal agitation and spatial disorders generate strong spin fluctuations that suppress the long-range magnetic ordering. We develop an analytical equation for the equilibrium magnetization of two-dimensional…
We simulated the field-dependent magnetization m(H,T) and the uniform susceptibility \chi(H,T) of classical Heisenberg antiferromagnets in the chain and square-lattice geometry using Monte Carlo methods. The results confirm the singular…
In 1999 Berry and Keating showed that a regularization of the 1D classical Hamiltonian H = xp gives semiclassically the smooth counting function of the Riemann zeros. In this paper we first generalize this result by considering a phase…
The Schwinger boson mean field theory is applied to the quantum ferrimagnetic Heisenberg chain. There is a ferrimagnetic long range order in the ground state. We observe two branches of the low lying excitation and calculate the spin…
Renormalization of the spin-wave spectrum is discussed in a cubic ferromagnet with dipolar forces at $T_C\gg T\ge0$. First 1/S-corrections are considered in detail to the bare spectrum $\epsilon_{\bf k} = \sqrt{Dk^2 (Dk^2 +…
The current theoretical and experimental situation is reviewed for low-dimensional (layered and chain-like) insulating systems. Such systems possess a low magnetic transition temperature $T_M$ and pronounced short-range magnetic order above…
We extend a microscopic theory of polarization and magnetization to include the spin degree of freedom of the electrons, introducing a general spin orbit coupling and Zeeman interaction term in the Hamiltonian. At finite frequencies and…