High-resolution phonon energy shift measurements with the inelastic neutron spin echo technique

Abstract

The energy resolution of the conventional way of measuring a small change in a phonon dispersion curve using neutron scattering is restricted by the relatively coarse intrinsic resolution ellipsoid of the neutron triple-axis spectrometer (TAS). By implementing inelastic neutron spin echo on the host TAS using the Larmor precession of the neutron spin, the energy resolution of such measurements can be further improved without reducing the resolution ellipsoid. Measurements of the temperature-dependent phonon energy change are demonstrated using superconducting magnetic Wollaston prisms at the HB-1 instrument of the High-Flux Isotope Reactor at Oak Ridge National Laboratory, and the achievable resolution is <10 meV.

Determination of acoustic phonon anharmonicities via second-order Raman scattering in CuI

“…The experimentally determined TA L , TA X , LA L and LA X phonon energies at the respective temperature are shown in figures 4(a)-(d). The experimental data for the LA L mode shows a linear dependence, in agreement with results for other materials like Ge and NaI from [54][55][56]. The shift of the acoustic phonons from 10 K up to RT is in the range of 2-6 cm −1 and is significantly smaller compared to the shifts of the optical ones.…”

Neutron Spin‐Echo Instrumentation for Magnetic Scattering

“…[ 36 ] A recent development in the field of NSE‐TAS uses precession devices (PDs) with static fields (without RF) confined by superconducting Meissner shields to prismatic regions, also referred to as Wollaston prisms. [ 37,38 ] First experiments showed a promising performance, both in a measurement of the linewidths and energy renormalization of phonons in Ge [ 39 ] and in LD. [ 40 ]…”