Spontaneous magnetization in unitary superconductors with time reversal symmetry breaking

We report the study of spontaneous magnetization (i.e., spin-polarization) for time-reversal symmetry (TRS)-breaking superconductors with unitary pairing potentials, in absence external magnetic fields or Zeeman fields. Spin-singlet ($\Delta_s$) and spin-triplet ($\Delta_t$) pairings can coexist whose crystal structure lacks inversion symmetry. The TRS be spontaneously broken once a relative phase $\pm\pi/2$ is developed, forming TRS-breaking state ($\Delta_s\pm i\Delta_t$). demonstrate that such could give rise to spin-polarization help spin-orbit coupling. Our result provides an alternative explanation breaking, beyond current understanding phenomena noncentrosymmetric superconductors. experimental results Zr$_3$Ir CaPtAs are also discussed view our theory.