Superconductivity effects in hopping conductivity of single-crystal La2CuO4 with excess oxygen

Abstract The transition from variable-range hopping conductivity to simple activated one (the Arrhenius low) is observed in single-crystal La 2 CuO 4+δ as the temperature is decreased below T ⋍ 20 K . It is shown that this effect can be assigned to the presence of superconducting inclusions (of T c = 15−20 K) in insulating sample. The existence of such inclusions may be related to the well-known phase separation for La 2 CuO 4+δ .