Antiferromagnetic ordering and disappearance of pseudogap within the vortex core of Tl_2Ba_2CuO_{6+\delta}

TL;DR

This study uses spatially-resolved NMR to reveal antiferromagnetic order within vortex cores of Tl_2Ba_2CuO_{6+\delta} and shows the pseudogap disappears there, contrasting with the surrounding pseudogap state.

Contribution

It provides direct evidence of antiferromagnetic ordering in vortex cores and shows the pseudogap vanishes within these regions, advancing understanding of high-temperature superconductor physics.

Findings

AF spin correlation is enhanced in vortex cores

Cu spins order antiferromagnetically at T_N=20K in the core

Pseudogap disappears within the vortex core

Abstract

Spatially-resolved NMR is used to probe the magnetism in and around the vortex core of nearly optimally-doped Tl_2Ba_2CuO_{6+\delta} (T_c=85K). The NMR relaxation rate T_1^{-1} at ^{205}Tl site, at which antiferromagnetic (AF) fluctuation can be monitored sensitively, provides a direct evidence that the AF spin correlation is significantly enhanced in the vortex core region. In the core region Cu spins show a local AF ordering with moment ~ 0.1\mu_B parallel to the layers at T_N=20K. Above T_N the core region is in the paramagnetic state which is a reminiscence of the state above the pseudogap temperature (T*=120K), indicating that the pseudogap disappears within the core.