Low-energy excitations in impurity substituted CuGeO{sub 3}

Journal Article · Sun Apr 01 04:00:00 EDT 2001 · Physical Review B

DOI:https://doi.org/10.1103/PhysRevB.63.134414· OSTI ID:40205458

Jones, B R; Sushkov, A B; Musfeldt, J L; Wang, Y J; Revcolevschi, A; Dhalenne, G

We report far-infrared reflectance measurements of Zn- and Si-doped CuGeO{sub 3} single crystals as a function of applied magnetic field at low temperature. Overall, the low-energy far-infrared spectra are extraordinarily sensitive to the various phase boundaries in the H-T diagram, with the features being especially rich in the low-temperature dimerized state. Zn impurity substitution rapidly collapses the 44 cm{sup -1} zone-boundary spin Peierls gap, although broadened magnetic excitations are observed at the lightest doping level (0.2%) and a remnant is still observable at 0.7% substitution. In a 0.7% Si-doped sample, there is no evidence of the spin gap. Impurity substitution effects on the intensity of the 98 cm{sup -1} zone-folding mode are striking as well. The lightly doped Zn crystals display an enhanced response, and even at intermediate doping levels, the mode intensity is larger than that in the pristine material. The Si-doped sample also displays an increased intensity of the 98 cm{sup -1} mode in the spin Peierls phase relative to the pure material. The observed trends are discussed in terms of the effect of disorder on the spin gap and 98 cm{sup -1} mode, local oscillator strength sum rules, and broken selection rules.

• Sponsoring Organization: (US)
• OSTI ID: 40205458
• Journal Information: Physical Review B, Journal Name: Physical Review B Journal Issue: 13 Vol. 63; ISSN 0163-1829
• Publisher: The American Physical Society
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
MAGNETIC FIELDS
MONOCRYSTALS
OSCILLATOR STRENGTHS
SELECTION RULES
SPECTRA
SPIN
SUM RULES