Variable-range hopping conductivity in the copper-oxygen chains of La_3Sr_3Ca_8Cu_24O_41

TL;DR

This study demonstrates that La_3Sr_3Ca_8Cu_24O_41 exhibits variable-range hopping conductivity along its chains, with a transition to nearest-neighbor hopping near 300 K, highlighting its behavior as a one-dimensional disordered system.

Contribution

It provides experimental evidence of variable-range hopping conduction in a copper-oxygen chain compound and characterizes the temperature-dependent transition to nearest-neighbor hopping.

Findings

DC conductivity follows Mott's law of variable-range hopping from 35 to 280 K.

Frequency dependence of conductivity shows a power-law behavior with s ≈ 1.

Conduction mechanism shifts from variable-range to nearest-neighbor hopping around 300 K.

Abstract

We show that the spin chain/ladder compound La_3Sr_3Ca_8Cu_24O_41 is an insulator with hopping transport along the chains. In the temperature range 35 - 280 K, DC conductivity sigma_{DC}(T) follows Mott's law of variable-range hopping conduction; the frequency dependence has the form sigma(\nu, T) = \sigma_{DC}(T) + A(T)\nu^{s}, where s \approx 1. The conduction mechanism changes from variable-range hopping to nearest-neighbor hopping around T_{c} =300 K. The chain array thus behaves like a one-dimensional disordered system. Disorder is due to random structural distortions of chains induced by irregular coordination of the La/Sr/Ca ions.