Analysis of the paraconductivity in underdoped $L{a}_{2-x}S{r}_{x}Cu{O}_4$ thin films using high magnetic fields

Abstract

The contribution of superconducting fluctuations to the conductivity, or paraconductivity is studied in the underdoped regime of $L{a}_{2-x}S{r}_{x}Cu{O}_4$ cuprates. A perpendicular magnetic field up to 50 T 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 (AL) regime of Gaussian fluctuations close to the critical temperature. At higher temperature, the paraconductivity shows a power-law decrease in temperature (as $T^{-\alpha }$) as was previously shown for underdoped $YB{a}_{2}C{u}_3{O}_{7-\delta }$ and $B{i}_{2}S{r}_{2}CaC{u}_2{O}_{8+\delta }$ 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 $T_C$ in the pseudogap state.

10 pages, 3 figures, 1 bib file