Negative Hall coefficients of heavily overdoped La2-xSrxCuO4

TL;DR

This study investigates the Hall coefficient in La2-xSrxCuO4 thin films, revealing a sign change from positive to negative with increased doping, and correlates this with the disappearance of superconductivity, challenging previous findings.

Contribution

It demonstrates a smooth doping-induced sign change in the Hall coefficient and links it to the loss of superconductivity in heavily overdoped cuprates.

Findings

Hall coefficient becomes temperature independent at high doping

Sign change of R_H from positive to negative occurs between x=0.28 and 0.32

Superconductivity disappears when R_H is negative

Abstract

The Hall coefficient (R_H) is investigated along the in-plane direction for carefully prepared La_2-x_Sr_x_CuO_4_ thin films from x=0.08 to x=0.40. It is found that R_H becomes almost temperature independent around room temperature for x >= 0.24, and its sign smoothly changes from positive to negative between x = 0.28 and 0.32, showing contrasting behavior to previously reported results. This result indicates that the carrier can be doped smoothly across the hole- to electron-dominant regions. According to the sign change of R_H, superconductivity disappears for x >= 0.32 films, which suggests that a positive R_H is one of the necessary conditions for superconductivity in p-type cuprates.