Related papers: Quantum Nonlinear Sigma Model for Arbitrary Spin H…
We report a neutron scattering study of the long-wavelength dynamic spin correlations in the model two-dimensional $S=1/2$ square lattice Heisenberg antiferromagnets Sr$_2$CuO$_2$Cl$_2$ and Sr$_2$Cu$_3$O$_4$Cl$_2$. The characteristic energy…
In this second paper in a series, we show that the the general statistical approach to nonrelativistic quantum mechanics developed in the first paper yields a representation of quantum spin and magnetic moments based on classical…
Spin-$S$ Heisenberg quantum antiferromagnets on the Kagome lattice offer, when placed in a magnetic field, a fantastic playground to observe exotic phases of matter with (magnetic analogs of) superfluid, charge, bond or nematic orders, or a…
Quantum spin liquids (QSLs) represent an exotic quantum many-body state characterized by the suppression of long-range magnetic order due to strong quantum fluctuations. The kagome spin-1/2 antiferromagnet (AFM) is a prime candidate for…
We develop a consistent semiclassical theory of spin dynamics for an isotropic ferromagnet with a spin $ S=1$ taking into consideration both bilinear and biquadratic over spin operators exchange interaction. For such non-Heisenberg magnets,…
Using a recently developed method for calculating series expansions of the excitation spectra of quantum lattice models, we obtain the spin-wave spectra for square lattice, $S=1/2$ Heisenberg-Ising antiferromagnets. The calculated spin-wave…
We work out the magnetization and susceptibility of Heisenberg- and XXZ-model antiferromagnet spin-1/2 systems in $D$ dimensions under a rigorous constraint of single particle site occupancy. Quantum fluctuations are taken into account up…
We have used a combination of neutron resonant spin-echo and triple-axis spectroscopies to determine the energy, fine structure, and linewidth of the magnon resonance in the model spin-1/2 ladder antiferromagnet IPA-CuCl_3 at temperatures T…
Spin-1/2 kagome-lattice Heisenberg antiferromagnet is theoretically known to have a quantum spin liquid ground state, one of the frontiers of condensed matter physics. The search for the model substances has been continued for a long time,…
We discuss numerical results for the 1-D spin 1/2 antiferromagnetic Heisenberg model with next-to-nearest neighbour coupling and in the presence of an uniform magnetic field. The model develops zero frequency excitations at field dependent…
We study the spin stiffness of a one-dimensional quantum antiferromagnet in the whole range of system sizes $L$ and temperatures $T$. We show that for integer and half-odd integer spin case the stiffness differs fundamentally in its $L$ and…
We show that Quantum-Monte-Carlo calculations of the dynamic structure factor of the isotropic spin-1/2 antiferromagnetic chain at intermediate temperatures corroborate a picture of diffusive spin dynamics at finite frequencies in the…
The correlation length of the square-lattice spin-1/2 Heisenberg antiferromagnet is studied in the low-temperature (asymptotic-scaling) regime. Our novel approach combines a very efficient loop cluster algorithm -- operating directly in the…
We review random loop representations for the spin-1/2 quantum Heisenberg models, that are due to Toth (ferromagnet) and Aizenman-Nachtergaele (antiferromagnet). These representations can be extended to models that interpolate between the…
We study the low-temperature properties of S=1 and 1/2 alternating spin chains with antiferromagnetic nearest-neighbor exchange couplings using analytical techniques as well as a quantum Monte Carlo method. The spin-wave approach predicts…
The dimensional crossover in a spin-$S$ nearest neighbor Heisenberg antiferromagnet is discussed as it is tuned from a two-dimensional square lattice, of lattice spacing $a$, towards a spin chain by varying the width $L_y$ of a…
The exact 2-spinon part of the dynamic spin structure factor $S_{xx}(Q,\omega)$ for the one-dimensional $s$=1/2 $XXZ$ model at $T$=0 in the antiferromagnetically ordered phase is calculated using recent advances by Jimbo and Miwa in the…
We present a spin-rotation-invariant Green-function theory for the dynamic spin susceptibility in the spin-1/2 antiferromagnetic Heisenberg model on a stacked honeycomb lattice. Employing a generalized mean-field approximation for arbitrary…
A perturbation spin-wave theory for the quantum Heisenberg antiferromagnets on a square lattice is proposed to calculate the uniform static magnetic susceptibility at finite temperatures, where a divergence in the previous theories due to…
We present an analysis of high precision Monte Carlo data for the two dimensional S=1/2 quantum Heisenberg antiferromagnet up to $\xi = 95.7(3)$ obtained by the continuous time version of the loop algorithm. Our data are in good agreement…