Undoped high-Tc superconductivity in T’-La1.8Eu0.2CuO4+δ revealed by 63,65Cu and 139La NMR: Bulk superconductivity and antiferromagnetic fluctuations

Hideto Fukazawa, Seiya Ishiyama, Masato Goto, Shuhei Kanamaru, Kohki Ohashi, Takayuki Kawamata, Tadashi Adachi, Michihiro Hirata, Takahiko Sasaki, Yoji Koike, Yoh Kohori

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

We performed 63,65Cu and 139La NMR measurements of T’-La1.8Eu0.2CuO4+δ (T’-LECO) with the Nd2CuO4-type structure (so-called T’-structure). As a result, we detected the 63,65Cu NMR signal under finite magnetic fields and found superconductivity without antiferromagnetic (AF) order only in the reduced T’-LECO, where excess apical oxygen atoms are properly removed. This indicates that the intrinsic ground state of the ideal T’-LECO is a paramagnetic and superconducting (SC) state. Below Tc, the Knight shift was found to rapidly decrease, which indicates the emergence of bulk superconductivity due to spin-singlet Cooper pairs in the reduced T’-LECO. In the SC state of the reduced T’-LECO, moreover, a characteristic temperature dependence of the spin-lattice relaxation rate 1/T1 was observed, which implies the existence of nodal lines in the SC gap. These findings suggest that the superconductivity in the reduced T’-LECO probably has d-wave symmetry. In the normal state of the reduced T’-LECO, on the other hand, AF fluctuations were found to exist from the temperature dependence of 1/T1T, though no clear pseudogap behavior was observed. This suggests that the AF correlation plays a key role in the superconductivity of undoped high-Tc cuprate superconductors with the T’-structure.

Original languageEnglish
Pages (from-to)30-35
Number of pages6
JournalPhysica C: Superconductivity and its applications
Volume541
DOIs
Publication statusPublished - 2017 Oct 15

Keywords

  • High-T cuprate
  • Nuclear magnetic resonance
  • Superconductivity
  • T’-Structure

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering

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