(color online) Simulations of temperature dependence of upper critical field with different pair-breaking mechanisms. Panel (a) represents the scenario of purely orbital limitation. Panel (b) describes the purely paramagnetic-limited case without spin–orbit scattering. Panel (c) gives an example in which both mechanisms take effect and, the spin–orbit scattering effect is included. The results in panels (a) and (c) are based on Werthammer–Helfand–Hohenberg theory.^[55] denotes the strength of spin–orbit scattering. The Maki parameter^[56] α is defined by , where is the purely orbitally limited value at zero temperature, denotes the Pauli-paramagnetic limit.