FORMATION, MOTION AND SUPERCONDUCTIVITY OF LARGE BIPOLARONS

Ferroelectric materials, characterized by very large ratios of the static to optical dielectric constants, are unique in fulfilling a requirement for the formation of a multidimensional large bipolaron. Unlike the very compact “small” bipolarons that are found in various transition-metal oxides, “large” bipolarons are not so massive that they readily localize. Thus, a large bipolaron is a mobile charged boson. As such, large bipolarons may manifest superconductivity analogous to the superfluidity of mobile neutral bosons. Distinctive electronic and magnetic properties of large bipolarons in the normal-state and superconducting states are described and compared to observations in high-temperature superconductors. © 1991, Taylor & Francis Group, LLC. All rights reserved.