Origin of the low-temperature in-plane resistivity anomaly

Determine the origin of the sample-dependent low-temperature in-plane resistivity anomaly in lightly doped La2CuO4+δ with hole concentration p ≅ 0.03, including whether it is caused by macroscopic crystalline imperfections such as orthorhombic twin structures.

Background

For La2CuO4+δ with p ≅ 0.03, the in-plane resistivity increases rapidly below approximately 100 K, but this behavior cannot be described by the two-dimensional variable-range-hopping form associated with strong Anderson localization. The anomaly is strongly sample dependent, whereas the superconducting transition temperature does not correlate with its magnitude.

The paper argues that Anderson localization is therefore unlikely to be the cause and suggests instead that macroscopic crystalline imperfections, particularly twin structures in the orthorhombic phase, may be responsible. The physical origin remains unresolved, making its determination necessary for understanding charge transport in the antiferromagnetic–superconducting state.