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
- Country of Publication:
- United States
- Language:
- English
Similar Records
Far infrared optical properties of NbSe/sub 3/
Far-infrared properties of (TMTSF)/sub 2/ClO/sub 4/
Related Subjects
360104* -- Metals & Alloys-- Physical Properties
656102 -- Solid State Physics-- Superconductivity-- Acoustic
Electronic
Magnetic
Optical
& Thermal Phenomena-- (-1987)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CHALCOGENIDES
CORRELATIONS
CRYSTAL STRUCTURE
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTROMAGNETIC RADIATION
HETEROCYCLIC COMPOUNDS
INFRARED RADIATION
INFRARED SPECTRA
INFRARED SPECTROMETERS
KRAMERS-KRONIG CORRELATION
MEASURING INSTRUMENTS
NIOBIUM COMPOUNDS
NIOBIUM SELENIDES
OPTICAL PROPERTIES
ORGANIC COMPOUNDS
PHONONS
PHYSICAL PROPERTIES
QUASI PARTICLES
RADIATIONS
SELENIDES
SELENIUM COMPOUNDS
SPECTRA
SPECTROMETERS
SUPERCONDUCTIVITY
TEMPERATURE DEPENDENCE
TMTSF
TRANSITION ELEMENT COMPOUNDS