Abstract:
We study the structure of the superconducting order parameter in underdoped NaFe1−x1−xCoxxAs pnictides with Tc≈19−21Tc≈19−21 K related to the 111 family. Using incoherent multiple Andreev reflection effect spectroscopy of planar break junctions, we directly determine the magnitudes of the two microscopic superconducting order parameters: the small superconducting gap ΔS(0)ΔS(0), and possible edges of the large gap ΔL(0)ΔL(0) having an anisotropy in the abab plane at T≪TcT≪Tc, the corresponding characteristic ratios, as well as their temperature dependences. Additionally, we detect features of the tunneling dI(V)/dVdI(V)/dV spectra in NaFe1−x1−xCoxxAs at eV∗>2ΔL(0)eV∗>2ΔL(0), those irrelative to superconducting state, and discuss their origin.
Citation:
S. A. Kuzmichev, I. V. Morozov, A. I. Shilov, E. O. Rakhmanov, T. E. Kuzmicheva, “Multiple andreev reflection effect spectroscopy of underdoped NaFe1−xCoxAs single crystals”, Pis'ma v Zh. Èksper. Teoret. Fiz., 117:8 (2023), 614–619; JETP Letters, 117:8 (2023), 612–617