Paraconductivity of underdoped La2-xSrxCuO4 thin-film superconductors using high magnetic fields

International audienceThe contribution of superconducting fluctuations to the conductivity, or paraconductivity, is studied in the underdoped regime of La2-xSrxCuO4 cuprates. A perpendicular magnetic field up to 50T is applied to suppress the superconductivity and obtain the normal state resistivity, which is then used to calculate the paraconductivity. Surprisingly enough, it is consistent with a two-dimensional Aslamazov-Larkin regime of Gaussian fluctuations close to the critical temperature. At higher temperature, the paraconductivity exhibits a power-law decrease in temperature (as T-α ), as was previously shown for underdoped YBa2Cu3O7-δ and Bi2Sr2CaCu2O8+δ samples. Our observations are not consistent with the existence of Kosterlitz-Thouless fluctuations. This tends to indicate that the superconducting pair amplitude is not already defined above TC in the pseudogap state