Coexistence of antiferromagnetism and superconductivity within t-J model with strong correlations and nonzero spin polarization

The coexistence of antiferromagnetism with superconductivity is studied theoretically within the t-J model with the Zeeman term included. The strong electron correlations are accounted for by means of the extended Gutzwiller projection method within a statistically consistent approach proposed recently. The phase diagram on the band filling-magnetic field plane is shown, and subsequently the system properties are analyzed for the fixed band filling n = 0.97. In this regime, the results reflect principal qualitative features observed recently in selected heavy-fermion systems, namely, (i) with the increasing magnetic field the system evolves from coexisting antiferromagnetic-superconducting phase through antiferromagnetic phase toward polarized paramagnetic state and (ii) the onset of superconducting order suppresses partly the staggered moment. The superconducting gap has both the spin-singlet and the staggered-triplet components, a direct consequence of a coexistence of the superconducting state with antiferromagnetism.