Anomalous thermal decoherence in a quantum magnet measured with neutron spin-echo spectroscopy

TL;DR

This study uses neutron spin-echo spectroscopy to investigate temperature-dependent line broadening in a quantum magnet, revealing non-Lorentzian line shapes and demonstrating NRSE's capability to analyze quantum correlations directly in the time domain.

Contribution

The paper introduces the application of neutron-resonance spin-echo (NRSE) to resolve non-Lorentzian line shapes in quantum magnetic systems, expanding the experimental capabilities of NRSE beyond standard linewidth measurements.

Findings

NRSE can resolve non-Lorentzian line shapes in quantum magnets.

Temperature-dependent asymmetric broadening observed in Cu(NO3)2·2.5D2O.

NRSE provides direct access to time-domain correlations without convolution effects.

Abstract

The effect of temperature dependent asymmetric line broadening is investigated in Cu(NO$_3$)$_2\cdot$2.5D$_2$O, a model material for a 1-D bond alternating Heisenberg chain, using the high resolution neutron-resonance spin-echo (NRSE) technique. Inelastic neutron scattering experiments on dispersive excitations including phase sensitive measurements demonstrate the potential of NRSE to resolve line shapes, which are non-Lorentzian, opening up a new and hitherto unexplored class of experiments for the NRSE method beyond standard line width measurements. The particular advantage of NRSE is its direct access to the correlations in the time domain without convolution with the resolution function of the background spectrometer. This novel application of NRSE is very promising and establishes a basis for further experiments on different systems, since the results for Cu(NO$_3$)$_2\cdot$2.5D$_2$O are applicable to a broad range of quantum systems.