Superexchange Interaction and Magnetic Moment in Antiferromagnetic High-T_c Copper-oxide Superconductors

TL;DR

This study uses Cu-NMR to explore how antiferromagnetic interactions and doping influence superconductivity in high-Tc cuprates, revealing that AFM interactions are crucial for high-temperature superconductivity.

Contribution

It provides detailed insights into the doping dependence of AFM moments and superexchange interactions, highlighting their roles in high-Tc superconductivity.

Findings

AFM moment decreases with doping and collapses at N_h=0.17

AFM ordering temperature increases with out-of-plane coupling n

Superexchange J_in remains invariant or increases with doping

Abstract

Extensive Cu-NMR studies on multilayered high-Tc cuprates have deduced the following results;(1) Antiferromagnetic (AFM) moment M_{AFM} is decreased with doping, regardless of the number of CuO_2 layers n, and collapses around a carrier density N_h = 0.17. (2) The AFM ordering temperature is enhanced as the out-of-plane coupling J_{out} increases with increasing n. (3) The in-plane superexchange J_{in} is invariant with doping, but is even increased. (4) The dome shape of T_c from the underdoped to the overdoped regime with a maximum T_c at N_h = 0.22 does not depend on n, but its maximum value of T_c seems to depend on n moderately. The present results strongly suggest that the AFM interaction plays the vital role as the glue for the Cooper pairs, which will lead us to a genuine understanding of why the T_c of cuprate superconductors is so high.