Observation of a common symmetry for the pseudogap and the superconducting order parameter near the surface of underdoped YBCO

TL;DR

This study reveals that both the pseudogap and superconducting order parameter in underdoped YBCO exhibit a common |d+is|-like symmetry near the surface, with magnetic field suppressing the superconducting gap but not the pseudogap.

Contribution

It provides experimental evidence of a shared symmetry between the pseudogap and superconducting gap in underdoped YBCO near the surface.

Findings

Superconducting gap shows |d+is|-like symmetry at zero magnetic field.

Magnetic field suppresses the superconducting gap but not the pseudogap.

Both gaps exhibit the same angular dependence, indicating a common symmetry.

Abstract

Measurements of the angular dependence of conductance spectra in the a-b plane of underdoped YBCO junctions are reported. At zero magnetic field the superconducting gap shows a |d+is|-like symmetry. Application of a magnetic field strongly suppresses this gap leaving only the pseudogap feature which also shows a |d+is|-like angular dependence. We thus observe the same symmetry for the superconducting gap and the pseudogap characterizing the YBCO electrodes near the interface with the barrier. An H_{c2} value of about 5T of the secondary (is) order parameter can also be deduced from our results.