Sum rules and missing spectral weight in magnetic neutron scattering in the cuprates

Abstract

We present estimates in the Hubbard and Heisenberg models for the spectral weight in magnetic neutron scattering experiments on the cuprates. With the aid of spin-wave theory and the time dependent Gutzwiller approximation we discuss how the spectral weight is distributed among the different channels and between high and low energies. In addition to the well known total moment sum rule we discuss sum rules for each component of the dynamical structure factor tensor which are peculiar for spin 1/2 systems. The various factors that reduce the spectral weight at the relevant energies are singled out and analyzed like: shielding factors, weight at electronic energies, multimagnon process etc. Although about 10% ∼ 15% of the naively expected weight is detected in experiments after consideration of these factors the missing weight is within the experimental uncertainties. A large fraction of the spectral weight is hard to detect with present experimental conditions.

High-Energy Spin Excitations in the Electron-Doped SuperconductorPr0.88LaCe0.12CuO4−δwithTcWilson1, Li2, Woo3 et al. 2006Phys. Rev. Lett.5514681View full textAdd to dashboardCite

“…−1 ) [21]. Since the total moment sum rule for spin-1 2 Heisenberg model requires one-magnon fluctuating moment squared to be smaller than the ordered static moment squared [28], the observed high-energy spin-wavelike excitations are unlikely to arise from the small ordered moment.…”

Фрустрированный $J_{1}$-$J_{2}$-$J_{3}$ Квантовый Двумерный Антиферромагнетик В Сферически-Симметричном Самосогласованном Подходе

“…Важнейшая величина, получаемая из нейтронных экспериментов в купратах [6], [36]- [40], -это локальная восприимчивость χ 2D (ω), которая определяется как мнимая часть спи-новой восприимчивости, проинтегрированная по квазиимпульсу:…”

Neutron Scattering Studies of Antiferromagnetic Correlations in Cuprates

“…weight [26]; it is also a small fraction of the the total spectral weight that is actually measured (which is much reduced from that predicted by the sum rule [90]). Figure 8.18(a) presents a summary, from Sidis et al [18], of experimental results for E r from neutron scattering and for twice the superconducting gap maximum, 2∆ m , from other techniques.…”

“…One would expect the continuum of electron-hole excitations to cause significant damping [90]. Could it be that the antiphase relationship of spin correlations across a charge stripe acts to separate the spin and charge excitations in a manner similar to that in a one-dimensional system [281,282]?…”