Temperature Dependence of the Spin-Peierls Energy Gap and Anomalous Line Shapes in CuGeO${}_3$

Abstract

Neutron scattering measurements on a large single crystal of CuGeO${}_3$ have been used to determine the temperature-dependence of the spin-Peierls energy gap. While the power law behavior of the intensity of structural superlattice peaks is well fit by $I(\mathrm{T})\propto ({\mathrm{T}}_c-\mathrm{T}{)}^{2\beta }$ with an exponent of $\beta =0.33$, the exponent for the temperature dependence of the energy gap is significantly smaller than expected for conventional spin-Peierls materials. Usual scaling relations relate the energy gap to the superlattice reflection intensity as $\Delta (\mathrm{T})\propto I^a$ with $a=1/3$; the present results suggest an exponent of $a\approx 1/6$ for CuGeO${}_3$. Additional scattering cross-section is observed in constant-$q$ and constant-$E$ scans creating a long `tail' extending to higher energies relating to a proposed scattering continuum.

10 pages, RevTeX, 6 postscript figures included, also available from http://insti.physics.sunysb.edu/~mmartin/pubs.html

References in corpus (1)

• Study of the magnetic susceptibility in the spin-Peierls system CuGeO${}_3$

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