The Magnetic Origin of d-Wave High-Tc Superconductivity from Tunneling Spectroscopy Measurements on Bi2212 Single Crystals

TL;DR

This paper presents a comprehensive experimental analysis of high-Tc superconductivity in Bi2212 crystals, revealing that d-wave superconductivity is mediated by spin-waves and involves multiple coexisting gaps.

Contribution

It introduces a detailed tunneling spectroscopy-based scenario showing magnetic and spinon pairing mechanisms as origins of high-Tc superconductivity in cuprates.

Findings

Identification of four distinct gaps below Tc.

Evidence that d-wave superconductivity is mediated by spin-waves.

Observation that the spinon pairing gap is larger but less intense than the d-wave gap.

Abstract

The complete scenario of high-Tc superconductivity based on experimental data from electron-tunneling spectroscopy on underdoped, overdoped and Ni-doped Bi2212 single crystals using a break-junction technique is presented. There are two different types of superconductivity in cuprates: superconductivity due to pairing of spinons on charged stripes and magnetic superconductivity mediated by spin-waves. The coherent state of the spinon superconductivity is established via the magnetic superconductivity. In NCCO, there is only the spinon superconductivity and the coherent state is established due to the Josephson coupling between charged stripes. Below Tc, we observe four different gaps, namely, (i) a SDW gap due to antiferromagnetic correlations; (ii) a superconducting gap due to spinon pairing; (iii) a d-wave magnetic superconducting gap, and (iv) a small superconducting gap most likely having g-wave symmetry. We show that the d-wave superconductivity is mediated by spin-waves and the magnitude of the superconducting gap due to pairing of spinons is larger than the magnitude of the d-wave gap, however, the d-wave gap is more intense. The superconducting gap due to pairing of spinons most likely has a s-wave symmetry. The maximum magnitudes of the SDW, the spinon and d-wave gaps are located at (p/2, p/2), (p/2, p/2) and (p, 0) on the Fermi surface, respectively. The d-g-wave superconductivity mediated by spin-waves can be considered as a pairing of magnetic polarons. We formulate a theorem for cuprates by analogy with the Anderson's theorem for classical superconductors. The presented model of high-Tc superconductivity naturally explains other experimental data.