Infrared spectroscopy of the intermediate-valence semiconductor YbB{sub 12}

Journal Article · Fri Dec 15 00:00:00 EST 2006 · Journal of Experimental and Theoretical Physics

DOI:https://doi.org/10.1134/S1063776106120077· OSTI ID:21067587

Prokhorov, A S; Spektor, I E; Volkov, A A ^[1]; Dressel, M ^[2]; Iga, F ^[3]

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1. Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation)
2. Universitaet Stuttgart, Physikalisches Institut (Germany)
3. Hiroshima University, Graduate School of ADSM (Japan)

The dynamic conductivity and permittivity spectra of the intermediate-valence compound YbB{sub 12} are measured in the frequency range (6-10{sup 4}) cm{sup -1} (quantum energy 0.75 meV-1.24 eV) at temperatures of 5-300 K. Analysis of the spectral singularities associated with the response of free charge carriers has made it possible for the first time to determine the temperature dependences of their microscopic parameters, viz., concentration, effective mass, relaxation frequency and time, mobility, and plasma frequency. It is shown that the relaxation frequency decreases upon cooling from 300 K to the coherence temperature T* = 70 K for YbB{sub 12}, which is mainly associated with the phonon mechanism of scattering of charge carriers. For cooling below the coherence temperature T* = 70 K, the temperature dependence of the relaxation frequency for charge carriers of the Fermi-liquid type is found to be {gamma} {approx} {gamma}{sub 0} + T{sup 2}, while their effective mass and relaxation time increase, respectively, to m*(20 K) = 34m{sub 0} (m{sub 0} is the free electron mass) and {tau}(20 K) = 4 x 10{sup -13} s, indicating the establishment of coherent scattering of carriers from localized magnetic moments of the f centers. At a temperature of T = 5 K, the conductivity spectrum contains an absorption line at a frequency of 22 cm{sup -1} (2.7 meV); the origin of this line can be associated with the exciton-polaron bound state. Since such a state was observed earlier in other intermediate-valence semiconductors (such as SmB{sub 6}, TmSe{sub 1-x}Te, and (Sm, Y)S), it is probably typical of this class of compounds.

• OSTI ID: 21067587
• Journal Information: Journal of Experimental and Theoretical Physics, Vol. 103, Issue 6; Other Information: DOI: 10.1134/S1063776106120077; Copyright (c) 2006 Nauka/Interperiodica; Article Copyright (c) 2006 Pleiades Publishing, Inc; Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-7761
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ABSORPTION SPECTROSCOPY
CHARGE CARRIERS
COHERENT SCATTERING
EFFECTIVE MASS
F CENTERS
INFRARED SPECTRA
LANGMUIR FREQUENCY
MAGNETIC MOMENTS
PERMITTIVITY
PHONONS
SAMARIUM BORIDES
SAMARIUM SULFIDES
SELENIUM TELLURIDES
SEMICONDUCTOR MATERIALS
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0000-0013 K
TEMPERATURE RANGE 0013-0065 K
TEMPERATURE RANGE 0065-0273 K
THULIUM TELLURIDES
YTTRIUM SULFIDES