Far-infrared absorptivity of the superconducting state of YBa[sub 2]Cu[sub 3]O[sub 7-[delta]] crystals

Miscellaneous · Wed Jan 01 00:00:00 EST 1992

OSTI ID:6888854

Pham, Thi

Measurements and analysis of the absorptivity A([omega]) are reported, for a series of YBa[sub 2]Cu[sub 3]O[sub 7[minus][delta]] crystals at the fixed temperature of 2K and in the frequency range from 80 to 650 cm[sup [minus]1] (10 and 80 meV). The focus is on twin-free crystals where the crystallographic axes are uniformly aligned throughout the sample. The measured absorptivity is finite in the vicinity of 3.5 k[sub B]Tc (230 cm[sup [minus]1]) and anisotropic. For radiation polarized along the crystallographic a-axis of the twin-free YBa[sub 2]Cu[sub 3]O[sub 7[minus][delta]] crystals the absorptivity is [approximately]0.5% with structures it begins an approximately linear rise near 310 cm[sup [minus]1]. From A([omega]) and published reflectivity data the real part of the conductivity [sigma][sub 1]([omega]) is obtained by a Kramers-Kronig analysis. The line-shape of a phonon at 350 cm[sup [minus]1] is asymmetric indicating a Fano effect. Three features at high frequencies 400-550 cm[sup [minus]1] are consistent with phonons shifted upward by [approximately]315 cm[sup [minus]1]. These observations are consistent with an order parameter gap 2[Delta] being near 315 cm[sup [minus]]. Below 2[Delta] spectral features appear to be phonon-related but have large oscillator strengths compared to the corresponding infrared-active phonons above Tc. The implications of the experimental observations are discussed.

• Research Organization: Maryland Univ., College Park, MD (United States)
• OSTI ID: 6888854
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM OXIDES
ABSORPTIVITY
COPPER OXIDES
YTTRIUM OXIDES
FAR INFRARED RADIATION
HIGH-TC SUPERCONDUCTORS
INTERMETALLIC COMPOUNDS
OPACITY
ALKALINE EARTH METAL COMPOUNDS
ALLOYS
BARIUM COMPOUNDS
CHALCOGENIDES
COPPER COMPOUNDS
ELECTROMAGNETIC RADIATION
INFRARED RADIATION
OPTICAL PROPERTIES
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RADIATIONS
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties