Robust dx2-y2 pairing symmetry in high-temperature superconductors

TL;DR

This study demonstrates that the dx2-y2 pairing symmetry in high-temperature cuprate superconductors remains consistent across various doping levels, highlighting the robustness of this pairing symmetry and its relation to Coulomb repulsion.

Contribution

It provides phase-sensitive evidence that dx2-y2 pairing symmetry persists across underdoped, optimally doped, and overdoped regimes in multiple cuprate systems.

Findings

dx2-y2 pairing symmetry is robust over doping variations

Time-reversal invariant pairing symmetry confirmed

Highlights role of Coulomb repulsion in superconductivity

Abstract

Although initially quite controversial, it has been widely accepted that the Cooper pairs in optimally doped cuprate superconductors have predominantly dx2-y2 wavefunction symmetry. The controversy has now shifted to whether the high-Tc pairing symmetry changes away from optimal doping. Here we present phase-sensitive tricrystal experiments on three cuprate systems: Y0.7Ca0.3Ba2Cu3O7-x (Ca-doped Y-123), La2-xSrxCuO4 (La-214) and Bi2Sr2CaCu2O8+x (Bi-2212),with doping levels covering the underdoped, optimal and overdoped regions. Our work implies that time-reversal invariant, predominantly dx2-y2 pairing symmetry is robust over a large variation in doping, and underscores the important role of on-site Coulomb repulsion in the making of high-temperature superconductivity.