Fig. 3: B versus T phase diagram for the Nd0.8Sr0.2NiO2.
From: Rotational symmetry breaking in superconducting nickelate Nd0.8Sr0.2NiO2 films
a B versus T phase diagram for in-plane magnetic fields. The white region above Bc||,0°onset(T) (open circles) represents the normal state, and the dark blue region below Bc||,0°1%(T) (open triangles) denotes the zero-resistance state (defined by R < 1% of RN). Between Bc||,0°onset and Bc||,0°1%(T) is the superconducting transition region, which is separated into ~isotropy (gray area), C4 (blue area), and C4 + C2 (pink area) regions from small-magnetic-field to large-magnetic-field regime, depending on whether the measured R(φ) curves exhibit nearly isotropy, C4 or C4 + C2 rotational symmetry. Bc||,0°50%(T) (black dots) and Bc||,45°50%(T) (red dots) represent the critical field along the a/b-axis (0°) and the ab diagonal direction (45°) determined by the 50% RN criterion, respectively. The blue solid line is the 2D G-L fit of the Bc||,0°50%(T) data near Tc. The Bc||,0°50%(T) and Bc||,45°50%(T) data are from sample S2, which show a more prominent upturn in the low-temperature regime. b–e The representative R(φ) curves at 3 K and 15 T in the polar plot (b) and rectangular plot (c), 8.5 K and 8 T in the polar plot (d) and 10.8 K and 2 T in the polar plot (e), manifesting different rotational anisotropies. φ represents the azimuthal angle between the magnetic field and the a/b-axis of the Nd0.8Sr0.2NiO2. The light blue area in b is a guide to the eye, representing the C2 anisotropy. The black arrows in this figure approximately mark the temperature and magnetic field positions in the phase diagram where the R(φ) curves are measured.
