Lineshapes of dynamical correlation functions in Heisenberg chains

Abstract

Preprint. Typeset using REVT E XWe calculate line shapes of correlation functions by use of complete diagonalization data of finite chains and analytical implications from conformal field theory, density of states, and Bethe ansatz. The numerical data have different finite size accuracy in case of the imaginary and real parts in the frequency and time representations of spin-correlation functions, respectively. The low temperature, conformally invariant regime crosses over at T * ≈ 0.7J to a diffusive regime that in turn connects continuously to the high temperature, interacting fermion regime. The first moment sum rule is determined.

Low-temperature electronic properties ofSr2RuO4.I. Microscopic model and normal-state properties

“…The scale invariance has been observed experimentally outside the Fermi liquid regime 29 and suggests values of 1/2 ≤ x ≤ 5/8 for Sr 2 RuO 4 . Note that these values of x describe a XXZ Heisenberg chain near the isotropic point, 71 i.e., J > ∼ J z for in-plane (J) and out-ofplane (J z ) magnetic coupling, 70 and are thus in quantitative agreement with the intermediate coupling regime assumed for Sr 2 RuO 4 within this approach.…”

“…Please refer to Ref. 70 for details. The limits of the applicability of the result from conformal field theory can be understood in the framework of studies of Heisenberg chains performed in Ref.…”

“…The limits of the applicability of the result from conformal field theory can be understood in the framework of studies of Heisenberg chains performed in Ref. 70. It has been shown that the effective scaling dimension x is temperature dependent.…”

“…For ω ∼ v eff effects from the upper continuum limit become relevant 70 voiding the direct applicability of Eq. (33) for ω > ∼ 10 meV.…”

Spin dynamics and coherent tunnelling in the molecular magnetic rings Fe $ \mathsf {_6}$ and Fe $ \mathsf {_8}$

“…The spin dynamics of rings with AF Heisenberg interactions has attracted some recent interest (see Refs. [22,23] and references therein). However, previous studies have been restricted to systems without anisotropy, which are not expected to show mesoscopic quantum phenomena in the form of coherent Néel vector tunneling.…”