Anomalous dynamical line shapes in a quantum magnet at finite temperature

TitleAnomalous dynamical line shapes in a quantum magnet at finite temperature
Publication TypeJournal Article
Year of Publication2012
AuthorsTennant DA, Lake B, James AJA, Essler FHL, Notbohm S, Mikeska HJ, Fielden J, Kogerler P, Canfield PC, Telling MTF
Journal TitlePhysical Review B
Date Published01
Type of ArticleArticle
ISBN Number1098-0121
Accession NumberWOS:000298861900001
Keywordschain, spin

The effect of thermal fluctuations on the dynamics of a gapped quantum magnet is studied using inelastic neutron scattering on copper nitrate, a model material for the spin-1/2, one-dimensional (1D) bond alternating Heisenberg chain. A large, highly deuterated, single-crystal sample of copper nitrate is produced using a solution growth method and measurements are made using the high-resolution backscattering spectrometer OSIRIS at the ISIS Facility. Theoretical calculations and numerical analysis are combined to interpret the physical origin of the thermal effects observed in the magnetic spectra. The primary observations are (1) a thermally induced central peak due to intraband scattering, which is similar to Villain scattering familiar from soliton systems in 1D, and (2) the one-magnon quasiparticle pole is seen to develop with temperature into an asymmetric continuum of scattering. We relate this asymmetric line broadening to a thermal strongly correlated state caused by hard-core constraints and quasiparticle interactions. These findings are a counter example to recent assertions of the universality of line broadening in 1D systems and are applicable to a broad range of quantum systems.

URL<Go to ISI>://WOS:000298861900001
Alternate JournalPhys. Rev. B