Crossover of the spectral weight function: A new interpretation of some large q neutron scattering data (abstract)

Abstract

Dynamic scaling theory proposed by Halperin and Hohenberg has been successfully applied to small q neutron scattering data in the past. However, some large q constant E scan neutron scattering data on Fe1 and Ni2 cannot be explained by the dynamic scaling theory with a Lorentzian spectral weight function. Here we proposed that the spectral weight function crosses over to a Gaussian function at large q. With this crossover hypothesis, we were able to explain the qw vs q0 behavior in the constant E scan data, and the discrepancy in the material-dependent constant A, obtained from large and small q data. The physical origin of this crossover phenomena can be explained as follows. At large q, each neutron probes a small region in the sample, and the overall effect will be an inhomogeneously broadened line shape, namely a Gaussian spectral weight function. Recently Folk and Iro3 proposed an asymptoic RG theory approach to explain the discrepancies between large q neutron data and the dynamic scaling theory. Our proposed Gaussian line-shape function is in excellent agreement with the line-shape function obtained by Folk and Iro at large q.