Antiferromagnetic Vortex Core of Tl_2Ba_2CuO_{6+x} Studied by Nuclear Magnetic Resonance

TL;DR

This study uses spatially-resolved NMR to reveal that antiferromagnetic spin correlations are enhanced in the vortex cores of Tl_2Ba_2CuO_{6+x}, showing local AF order below 20K and pseudogap disappearance within cores.

Contribution

It provides direct NMR evidence of antiferromagnetic order in vortex cores of a cuprate superconductor, highlighting the interplay between magnetism and superconductivity.

Findings

AF spin correlation is enhanced in vortex cores.

Cu spins show local AF order below 20K.

Pseudogap disappears within vortex cores.

Abstract

Spatially-resolved NMR is used to probe the magnetism in and around vortex cores of nearly optimally-doped Tl_2Ba_2CuO_{6+x} (Tc=85 K). The NMR relaxation rate 1/T_1 at Tl site 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 moments 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*~120 K), indicating that the pseudogap disappears within cores.