Effect of lattice instability on superconductivity in sodium tungsten bronze
The effect of lattice instability on the electronic properties of the tungsten bronzes, M/subx/WO$sub 3$(0 < x < 1), is considered. A model of the free energy which describes the various phases as local minima in configuration space is shown to provide a basis for understanding observed and transformations them where M is an alkali metal. For the case of Na/subx/WO$sub 3$, the effect on the superconducting transition temperature of a phonon which is assumed to soften as a function of x is explicitly calculated. Tunneling between the local free-energy minima is assisted by this soft phonon. Good agreement is obtained with recent experimental observations of a dramatic increase in T/subc/ as x decreases and approaches the critical value for transition between the superconducting and semiconducting tetragonal phases. Noteworthy features of this work are that the structural transformation does not correspond to a simple condensation of the soft phonon, and also that the phonon softening and configurational tunneling are considered simultaneously. (AIP)
- Research Organization:
- Naval Research Laboratory, Washington, D.C. 20375
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-33-023693
- OSTI ID:
- 4051725
- Journal Information:
- Phys. Rev., B, v. 13, no. 3, pp. 1032-1039, Journal Name: Phys. Rev., B, v. 13, no. 3, pp. 1032-1039; ISSN PLRBA
- Country of Publication:
- United States
- Language:
- English
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*TUNGSTEN OXIDES-- SUPERCONDUCTIVITY
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Cermets & Refractories-- Physical Properties
ELECTRICAL PROPERTIES
LATTICE VIBRATIONS
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Ceramics
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Structure & Phase Studies
N66200 --Physics (Low Temperature)--Superconductivity
PHONONS
SODIUM COMPOUNDS
SUPERCONDUCTORS
TRANSITION TEMPERATURE
TUNNEL EFFECT