Fig. 1: Structure and the quasi-two-dimensional superconductivity in Nd0.8Sr0.2NiO2.
From: Rotational symmetry breaking in superconducting nickelate Nd0.8Sr0.2NiO2 films
a Crystal structure of the infinite-layer nickelate Nd0.8Sr0.2NiO2. b Temperature dependence of the resistance R(T) at zero magnetic field from 2 K to 300 K. The inset shows the R(T) curves below 20 K at 0 T (black circles), B∥ = 16 T (red circles), and B⊥ = 16 T (purple circles). Here, the B∥ is applied along the a/b-axis and B⊥ is along the c-axis. The blue solid line represents the BKT transition fitting using the Halperin-Nelson equation. c Schematic image and optical photo (inset) of the Corbino-disk configuration for polar (θ) angular dependent magnetoresistance R(θ) measurements on the Nd0.8Sr0.2NiO2 thin film. Here, θ represents the angle between the magnetic field and the c-axis of the Nd0.8Sr0.2NiO2. d Temperature dependence of the critical magnetic field Bc(T) for the magnetic fields along the c-axis (denoted as ⊥), the a/b-axis (∥, 0°), and the ab diagonal direction (∥, 45°). Here, the Bc is defined as the magnetic field corresponding to 50% normal state resistance. The blue and the orange solid lines are the 2D G-L fittings of the Bc(T) data near Tc. e Polar angular dependence of the critical magnetic field Bc(θ) at T = 6 K. The inset shows a close-up of the Bc(θ) around θ = 90°. The red solid line and the blue solid line are the fittings with the 2D Tinkham model (Bc(θ)sin(θ)/Bc||)2 + |Bc(θ)cos(θ)/Bc⊥| =1 and the 3D anisotropic mass model Bc(θ) = Bc||/(sin2(θ) + γ2cos2(θ))1/2 with γ = Bc||/Bc⊥, respectively. f, g Representative polar angular dependence of the magnetoresistance R(θ) at temperature T = 5 K under B = 12 T (f) and B = 8 T (g).
