Analysis of the paraconductivity in underdoped $La_{2-x}Sr_xCuO_4$ thin films using high magnetic fields

TL;DR

This study investigates the paraconductivity in underdoped La2-xSrxCuO4 thin films under high magnetic fields, revealing a two-dimensional Gaussian fluctuation regime near Tc and a power-law decay at higher temperatures, challenging the Kosterlitz-Thouless fluctuation model.

Contribution

It provides experimental evidence that the paraconductivity in underdoped La2-xSrxCuO4 aligns with a 2D Gaussian fluctuation model and refutes the presence of Kosterlitz-Thouless fluctuations above Tc.

Findings

Paraconductivity consistent with 2D Aslamazov-Larkin regime near Tc

Power-law decay of paraconductivity at higher temperatures

Absence of Kosterlitz-Thouless fluctuations above Tc

Abstract

The contribution of superconducting fluctuations to the conductivity, or paraconductivity is studied in the underdoped regime of $La_{2-x}Sr_xCuO_4$ 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 $YBa_2Cu_3O_{7-\delta}$ and $Bi_2Sr_2CaCu_2O_{8+\delta}$ 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.