Triple sign reversal of Hall effect in HgBa_{2}CaCu_{2}O_{6} thin films after heavy-ion irradiations

TL;DR

This study reports the first observation of triple sign reversal in the Hall effect of ion-irradiated HgBa_{2}CaCu_{2}O_{6} thin films, linking it to changes in the density of states and superconducting gap due to irradiation.

Contribution

It demonstrates the occurrence of triple sign reversal in the Hall effect of high-T_c superconductor thin films after heavy-ion irradiation, supported by a theoretical explanation involving density of states.

Findings

Triple sign reversal observed in Hall effect

Negative dip more pronounced at higher fields

Reversal explained by density of states derivative

Abstract

Triple sign reversal in the mixed-state Hall effect has been observed for the first time in ion-irradiated HgBa_{2}CaCu_{2}O_{6} thin films. The negative dip at the third sign reversal is more pronounced for higher fields, which is opposite to the case of the first sign reversal near T_c in most high-T_c superconductors. These observations can be explained by a recent prediction in which the third sign reversal is attributed to the energy derivative of the density of states and to a temperature-dependent function related to the superconducting energy gap. These contributions prominently appear in cases where the mean free path is significantly decreased, such as our case of ion-irradiated thin films.