Physical Review Letters
Extended Universal Finite- T Renormalization of Excitations in a Class of One-Dimensional Quantum Magnets
A. Zheludev, Vasile Ovidiu Garlea, L. P. Régnault, Hirotaka Manaka, Alexei M. Tsvelik, Jae-Ho Chung
Abstract
Temperature dependencies of gap energies and magnon lifetimes are measured in the quasi-one-dimensional $S=1/2$ gapped quantum magnets $({\mathrm{CH}}_{3}{)}_{2}{\mathrm{CHNH}}_{3}{\mathrm{CuCL}}_{3}$ ($\mathrm{IPA}\mathrm{\text{\ensuremath{-}}}{\mathrm{CuCl}}_{3}$, where IPA denotes isopropyl ammonium) and ${\mathrm{Cu}}_{2}{\mathrm{Cl}}_{4}\ifmmode\cdot\else\textperiodcentered\fi{}{\mathrm{D}}_{8}{\mathrm{C}}_{4}{\mathrm{SO}}_{2}$ ($\mathrm{Sul}\mathrm{\text{\ensuremath{-}}}{\mathrm{Cu}}_{2}{\mathrm{Cl}}_{4}$) using inelastic neutron scattering. The results are compared to those found in literature for $S=1$ Haldane spin chain materials and to theoretical calculations for the $O(3)$- and $O(N)$- quantum nonlinear $\ensuremath{\sigma}$-models. It is found that when the $T=0$ energy gap $\ensuremath{\Delta}$ is used as the temperature scale, all experimental and theoretical curves are identical to within system-dependent but temperature-independent scaling factors of the order of unity. This quasi-universality extends over a surprising broad $T$ range, at least up to $\ensuremath{\kappa}T\ensuremath{\sim}1.5\ensuremath{\Delta}$.