Physical review. B, Solid state
Space-time—dependent spin correlation of the one-dimensional Ising model with a transverse field. Application to higher dimensions
Janine Lajzerowicz, Pierre M. Pfeuty
Abstract
The correlation functions ${\ensuremath{\rho}}_{\mathrm{xx}}(R,t)$ and ${\ensuremath{\rho}}_{\mathrm{yy}}(R,t)$ are calculated for the one-dimensional Ising model with a transverse field $h$ at $T=0$. This model corresponds to the $X Y$ model with $\ensuremath{\gamma}=1$, and is equivalent to the two-dimensional anisotropic (${J}_{1}\ensuremath{\rightarrow}\ensuremath{\infty}$, ${J}_{2}\ensuremath{\rightarrow}0$) Ising model. The additional dimension in the classical model is the imaginary time of the quantum model. For all values of $h$, ${\ensuremath{\rho}}_{\mathrm{yy}}(R,t)=\ensuremath{-}(\frac{1}{{h}^{2}})(\frac{{\ensuremath{\partial}}^{2}}{\ensuremath{\partial}{t}^{2}}){\ensuremath{\rho}}_{\mathrm{xx}}(R,t)$. At the critical field $h={h}_{c}=1$, ${\ensuremath{\rho}}_{\mathrm{xx}}(R,t)\ensuremath{\sim}{({R}^{2}\ensuremath{-}{t}^{2})}^{\frac{\ensuremath{-}1}{8}}$. For $h<1,h>1$ the results already obtained for the $\mathrm{XY}$ model are recovered. We give some consequences from this equivalence in higher dimension, concerning the behavior of the correlation function at the critical field at $T=0$.