Infrared optical properties of the quasi-one-dimensional conductors NbSe/sub 3/ and (TMTSF)/sub 2/ClO/sub 4/

Thesis/Dissertation · Fri Dec 31 23:00:00 EST 1982

OSTI ID:5678083

Challener, IV, W A

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/. These compounds are members of a novel class of materials called quasi-one-dimensional conductors. 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. A Kramers-Kronig analysis has been done of the far infrared reflectance of NbSe/sub 3/ to obtain an estimate of the optical constants. Models of the frequency dependent conductivity have been used 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. The far infrared reflectance of (TMTSF)/sub 2/ClO/sub 4/ has been measured and a Kramers-Kronig analysis has been performed 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/. There is no explanation at present for the large peak, but it is believed 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.

• OSTI ID: 5678083
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
CARBON COMPOUNDS
CHALCOGENIDES
CHARGE DENSITY
CORRELATIONS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTROMAGNETIC RADIATION
ENERGY
FAR INFRARED RADIATION
HALOGEN COMPOUNDS
HETEROCYCLIC COMPOUNDS
INFRARED RADIATION
IODINE COMPOUNDS
KRAMERS-KRONIG CORRELATION
NIOBIUM COMPOUNDS
NIOBIUM SELENIDES
OPTICAL PROPERTIES
ORGANIC COMPOUNDS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
PHYSICAL RADIATION EFFECTS
RADIATION EFFECTS
RADIATIONS
REFRACTORY METAL COMPOUNDS
SELENIDES
SELENIUM COMPOUNDS
SPECTROSCOPY
SUPERCONDUCTIVITY
TEMPERATURE DEPENDENCE
TMTSF
TRANSITION ELEMENT COMPOUNDS