Optical conductivity of single crystals of Ba[sub 1[minus]x]M[sub x]BiO[sub 3]/ (M = K, Rb, x = 0. 04, 0. 37)

Journal Article · Fri Oct 01 00:00:00 EDT 1993 · Journal of Superconductivity; (United States)

DOI:https://doi.org/10.1007/BF00617482· OSTI ID:5121537

Guha, S; Peebles, D; Browning, V; Wieting, T ^[1]; Chandler-Horowitz, D ^[2]; Norton, M ^[3]

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1. Naval Research Lab., Washington, DC (United States)
2. National Inst. of Standards and Technology, MD (United States)
3. Marshall Univ., Huntington, WV (United States)

Reflectance data (0.001-4.0 eV) from several large (a typical surface area 3 x 3 mm[sup 2]) single crystals of Ba[sup 1[minus]x]K[sub x]BiO[sub 3] (x = 0.04, 0.37) (BKBO) and Ba[sub 1[minus]x]Rb[sub x]BiO[sub 3](x = 0.37) (BRBO) were obtained by Fourier transform infrared (FTIR) and ellipsometric methods. Normal-state optical conductivities ([sigma][sub 1]) of these samples were obtained from infrared and ellipsometric measurements using a Kramers-Kronig transform. A broad mid-IR band was observed that peaked at 0.3 eV for BKBO and at 0.16 eV for BRBO at room temperature. Each band was fitted with two Lorentz oscillators. The optical mass of the charge carriers was obtained from a Drude fit, and was found to be large (m[sup *] = 28-33m[sub e]). These overdamped charge carriers can be viewed as polarons with a large effective mass. An optic phonon mode at 325 cm[sup [minus]1] was also observed in the metallic phase. This mode was identified as a disorder-induced lattice mode, and was strongly enhanced at 8 K, favoring a strong coupling between this phonon and itinerant electronic states. Low-frequency spectra between 10 and 400 cm[sup [minus]1] observed below the superconducting temperature indicated an energy gap that agreed with the BCS-type mechanism. Interpretations of low-temperature measurements on BKBO and BRBO were complicated due to the change of color of the sample from bluish-green to bronze-red. Upon warming, samples revert to their original bluish-green color. 12 refs., 9 figs., 2 tabs.

• OSTI ID: 5121537
• Journal Information: Journal of Superconductivity; (United States), Vol. 6:5; ISSN 0896-1107
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
HIGH-TC SUPERCONDUCTORS
ELECTRONIC STRUCTURE
INFRARED SPECTRA
OPTICAL PROPERTIES
INFRARED RADIATION
SPECTRAL REFLECTANCE
BARIUM COMPOUNDS
BISMUTH COMPOUNDS
CHARGE CARRIERS
COUPLING
CRYSTAL LATTICES
ELLIPSOMETRY
FOURIER TRANSFORM SPECTROMETERS
KRAMERS-KRONIG CORRELATION
LIGHT TRANSMISSION
MONOCRYSTALS
PHONONS
POLARONS
POTASSIUM COMPOUNDS
RUBIDIUM COMPOUNDS
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
CORRELATIONS
CRYSTAL STRUCTURE
CRYSTALS
ELECTROMAGNETIC RADIATION
MEASURING INSTRUMENTS
MEASURING METHODS
PHYSICAL PROPERTIES
QUASI PARTICLES
RADIATIONS
SPECTRA
SPECTROMETERS
SUPERCONDUCTORS
360207* - Ceramics
Cermets
& Refractories- Superconducting Properties- (1992-)
665411 - Basic Superconductivity Studies- (1992-)