title: Hopping conductivity in CaCu(2)O(3) single crystals.
abstract: The resistivity, ρ, of the spin-ladder compound CaCu(2)O(3) is investigated between T∼130-450 K. The ρ(T) data measured for [Formula: see text] (along the Cu-O-Cu leg) and [Formula: see text] (along the Cu-O-Cu rungs), ρ(a)(T)>ρ(b)(T), exhibit an activated dependence, similar in both directions and characterized by a nearest-neighbour hopping followed by a variable-range hopping (VRH) regime when T is decreased. A detailed analysis of ρ(T) demonstrates that conventional d-dimensional models of the hopping conductivity, based on the electron localization in disordered systems, cannot interpret the experimental data at any d = 1, 2 or 3, leading to the mismatch of the characteristic energies and/or unphysical values of the characteristic length scales. The observed VRH conductivity law on the low-temperature interval, lnρ∼T(-3/4), contradicts the models above, too. Instead, it is found that this law can be substantiated and the correct matching of the energy and length scales can be found within a model of Fogler et al (2004 Phys. Rev. B 69 035413) by treating CaCu(2)O(3) as a three-dimensional array of quasi-one-dimensional electron crystals.
authors.affiliation: Institute of Applied Physics, Academy of Sciences of Moldova, Academiei Street 5, MD-2028 Kishinev, Moldova.
authors.forename: K G
authors.initials: KG
authors.lastname: Lisunov
authors.forename: E
authors.initials: E
authors.lastname: Arushanov
authors.forename: B
authors.initials: B
authors.lastname: Raquet
authors.forename: J M
authors.initials: JM
authors.lastname: Broto
authors.forename: F C
authors.initials: FC
authors.lastname: Chou
authors.forename: N
authors.initials: N
authors.lastname: Wizent
authors.forename: G
authors.initials: G
authors.lastname: Behr