Far-infrared linear response and radio-frequency nonlinear response of charge-density-wave conductors and high-T sub c superconductors
The far-infrared linear response of the charge-density-wave (CDW) conductor (TaSe{sub 4}){sub 2}I and polycrystalline samples of the high-T{sub c} superconductors LaSr{sub 1.85}Ca{sub 0.15}CuO{sub 4} and La{sub 1.85}Ca{sub 0.15}CuO{sub 4} was measured. The frequency and temperature range of the measurements is 8-350 cm{sup {minus}1} and 5 to 300K. At low temperatures in (TaSe{sub 4}){sub 2}I, a mode with giant oscillator strength was found at 38 cm{sup {minus}1}. At low temperatures in the high-T{sub c} superconductors, a reflectance edge was observed near 2.5k{sub B} T{sub c}. The BCS-like temperature dependence of the reflectance edge is suggestive of an energy-gap interpretation. However, a simple model shows that a BCS-like temperature dependence is also consistent with an interpretation of the reflectance edge as a low-frequency plasmon. It is not yet possible to deduce the magnitude of the energy gap directly from the FIR spectra of polycrystalline sample. The radio-frequency nonlinear response of the CDW conductor NbSe{sub 3} was also measured. In the presence of combined rf- and dc-electric fields, mode locking occurs in NbSe{sub 3}. Complete mode locking in conventional samples is found to dramatically suppress sliding CDW conduction fluctuations.
- Research Organization:
- California Univ., Berkeley, CA (USA)
- OSTI ID:
- 7033806
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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