Infrared optical properties of the quasi-one-dimensional conductors NbSe/sub 3/ and (TMTSF)/sub 2/ClO/sub 4/
The technique of far-infrared Fourier-transform spectroscopy has been used to study the properties of two materials, NbSe/sub 3/ and (TMTSF)/sub 2/ClO/sub 4/. NbSe/sub 3/ undergoes incommensurate charge-density-wave (CDW) transitions and exhibits electrical transport by sliding CDW's. (TMTSF)/sub 2/ClO/sub 4/ undergoes order-disorder, spin-density-wave, and superconducting transitions at ambient pressure. It is a member of the first class of organic materials to be synthesized which exhibit superconductivity. We have done a Kramers-Kronig analysis of the far-infrared reflectance of NbSe/sub 3/ to obtain an estimate of the optical constants. We have used models of the frequency-dependent conductivity to fit the data. General arguments show that at 2K a CDW energy gap exists between 120 and 190 cm/sup -1/, the relaxation time(s) of the free carriers and CDW pinned mode is >3 x 10/sup -12/s, and the ratio of the free-carrier concentration to band mass is <2 x 10/sup 20/ cm/sup -3//m/sub 0/. The strength of the pinned mode obtained from the detailed fit is inconsistent with the classical model of CDW transport. We have also measured the far-infrared reflectance of (TMTSF)/sub 2/ClO/sub 4/ and performed a Kramers-Kronig analysis to obtain the optical constants. A large peak in the conductivity occurs above 100 cm/sup -1/, and a smaller peak occurs at approx. 25 cm/sup -1/. We have no explanation at present for the large peak, but we believe that the small peak is a phase phonon. It occurs when the orientations of the ClO/sub 4/ anions order and thereby induce a charge-density wave in the lattice. Our data, however, are inconsistent with an interpretation based upon a theory of quasi-one-dimensional fluctuational superconductivity.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5750127
- Report Number(s):
- LBL-16186; ON: DE84000940
- Resource Relation:
- Other Information: Thesis
- Country of Publication:
- United States
- Language:
- English
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Far infrared optical properties of NbSe/sub 3/
Related Subjects
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
NIOBIUM SELENIDES
OPTICAL PROPERTIES
SUPERCONDUCTIVITY
TMTSF
CRYSTAL STRUCTURE
ELECTRIC CONDUCTIVITY
INFRARED RADIATION
INFRARED SPECTRA
INFRARED SPECTROMETERS
KRAMERS-KRONIG CORRELATION
PHONONS
TEMPERATURE DEPENDENCE
CHALCOGENIDES
CORRELATIONS
ELECTRICAL PROPERTIES
ELECTROMAGNETIC RADIATION
HETEROCYCLIC COMPOUNDS
MEASURING INSTRUMENTS
NIOBIUM COMPOUNDS
ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
QUASI PARTICLES
RADIATIONS
SELENIDES
SELENIUM COMPOUNDS
SPECTRA
SPECTROMETERS
TRANSITION ELEMENT COMPOUNDS
360104* - Metals & Alloys- Physical Properties
656102 - Solid State Physics- Superconductivity- Acoustic
Electronic
Magnetic
Optical
& Thermal Phenomena- (-1987)