Abstract
The spectral densities of dynamical spin autocorrelation functions at infinite temperature are studied for the S=1/2XXZ model (with exchange couplings ${\mathit{J}}_{\mathit{x}}$=${\mathit{J}}_{\mathit{y}}$\ensuremath{\equiv}J,${\mathit{J}}_{\mathit{z}}$) on the linear chain, the square lattice, and the simple cubic lattice. The low-frequency behavior of a given spectral density is inferred from certain characteristic properties of its continued-fraction coefficients as determined from computed frequency moments. The analysis yields estimates for the ${\mathit{J}}_{\mathit{z}}$/J dependence of the infrared-singularity exponent. In the d=1 case, the exponent for spin fluctuations perpendicular to the O(2) symmetry axis responds sensitively as the anisotropy parameter sweeps across the O(3) symmetry point ${\mathit{J}}_{\mathit{z}}$/J=1, while the exponent for the parallel fluctuations shows little variation. In the cases d=2 and d=3 the same observations are made for autocorrelation functions of aggregate spins in chains and lattice planes, respectively.
Highlights
The phenomenological concept of diffusion of a conserved magnetization component was introduced more than four decades ago. 1 It has been very useful for the interpretation of experiments that probe the transport of spin fluctuations at high temperature
In the cases d = 2 and d = 3 the same observations are made for autocorrelation functions of aggregate spins in chains and lattice planes, respectively
We see at one glance that our indicator detects fairly reliably where site-spin autocorrelation functions describe one-dimensional diffusion, namely, for the d = 1 lattice only
Summary
Markus Bohm and Hajo Leschke lnstitut fii.r Theoretische Physik, Universitiit Erlangen-Nurnberg, D-91058 Erlangen, Germany. Martin Henneke Physikalisch-Technische Bundesanstalt, Abt. 8.1, D-38116 Braunschweig, Germany. The spectral densities of dynamical spin autocorrelation functions at infinite temperature are studied for the S = ~ XXZ model (with exchange couplings J., = Jy:::::: J, J,.) on the linear chain, the square lattice, and the simple cubic lattice. In the d = 1 case, the exponent for spin fluctuations perpendicular to the 0(2} symmetry axis responds sensitively as the anisotropy parameter sweeps across the 0(3}. / J 1, while the exponent for the parallel fluctuations shows little variation. In the cases d = 2 and d = 3 the same observations are made for autocorrelation functions of aggregate spins in chains and lattice planes, respectively
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.