Evolution of the resistivity anisotropy in Bi_{2}Sr_{2-x}La_{x}CuO_{6+\delta} single crystals for a wide range of hole doping

TL;DR

This study investigates how the resistivity anisotropy in Bi-based cuprate superconductors varies with hole doping and temperature, revealing the pseudogap's significant influence on anisotropic transport properties.

Contribution

It provides detailed measurements of resistivity anisotropy across a wide doping range, highlighting the pseudogap's role in the temperature dependence of anisotropic resistivity.

Findings

Resistivity anisotropy increases with decreasing doping, except in the most underdoped samples.

The pseudogap enhances anisotropy and causes rapid growth of /b with decreasing temperature.

Two distinct temperature regions in (T) suggest different mechanisms in the pseudogap phase.

Abstract

To elucidate how the temperature dependence of the resistivity anisotropy of the cuprate superconductors changes with hole doping, both the in-plane and the out-of-plane resistivities (\rho_{ab} and \rho_{c}) are measured in a series of high-quality Bi_{2}Sr_{2-x}La_{x}CuO_{6+\delta} (BSLCO) single crystals for a wide range of x (x = 0.23 - 1.02), which corresponds to the hole doping per Cu, p, of 0.03 - 0.18. The anisotropy ratio, \rho_{c}/\rho_{ab}, shows a systematic increase with decreasing p at moderate temperatures, except for the most underdoped composition where the localization effect enhances \rho_{ab} and thus lowers \rho_{c}/\rho_{ab}. The exact p dependence of \rho_{c}/\rho_{ab} at a fixed temperature is found to be quite peculiar, which is discussed to be due to the effect of the pseudogap that causes \rho_{c}/\rho_{ab} to be increasingly more enhanced as p is reduced. The pseudogap also causes a rapid growth of \rho_{c}/\rho_{ab} with decreasing temperature, and, as a result, the \rho_{c}/\rho_{ab} value almost reaches 10^6 in underdoped samples just above T_c. Furthermore, it is found that the temperature dependence of \rho_{c} of underdoped samples show two distinct temperature regions in the pseudogap phase, which suggests that the divergence of \rho_{c} below the pseudogap temperature is governed by two different mechanisms.