Normal State Ettingshausen Effect in La_{2-x}Sr_{x}CuO_{4}

TL;DR

This study introduces a measurement method for the Ettingshausen coefficient in high-T_c superconductor La_{2-x}Sr_{x}CuO_{4}, revealing its metallic behavior and sign change near a specific doping level, contrasting with other transport properties.

Contribution

A novel measurement technique was developed to accurately determine the Ettingshausen coefficient, eliminating thermal effects, and applied to La_{2-x}Sr_{x}CuO_{4} to uncover its doping-dependent behavior.

Findings

Ettingshausen coefficient is about 10^{-7} m^{3} K/J across doping levels.

The coefficient changes sign near x ≈ 0.07.

P shows weak variation compared to other transport coefficients.

Abstract

A method for measurements of small (metallic) Ettingshausen coefficient (P) was developed. The influence of the dominating thermal effects, the Joule and Thomson heats, was eliminated making use of the odd symmetry of the Ettingshausen temperature gradient in respect with reversing of the direction of the magnetic field and electrical current. The method was applied to La_{2-x}Sr_{x}CuO_{4} ($x=0.03\div 0.35$) high-T_c superconductor in normal state. We have found that in the whole composition range the Ettingshausen coefficient is of the order of 10^{-7} m^{3} K/J which is characteristic of typical metals. The coefficient changes sign from positive to negative near $x\approx 0.07$. Weak variation of P is in contrast to the behavior of other transport coefficients for La_{2-x}Sr_{x}CuO_{4}, as the thermoeletric power or the Hall coefficient, which have been reported in literature to change their values by more than two orders of magnitude with Sr doping.