Spin-Orbit Coupling-Induced Magnetic Phase in the d-Density-Wave Phase of La_2-xBa_xCuO₄ Superconductors

We study the effects of spin-orbit coupling in the d-density wave (DDW) phase. In the low-temperature orthorhombic phase of La_2-xBa_xCuO₄, we find that spin-orbit coupling induces ferromagnetic moments in the DDW phase, which are polarized along the [110] direction with a considerable magnitude. This effect does not exist in the superconducting phase. On the other hand, if the d-density wave order does not exist at zero field, a magnetic field along the [110] direction always induces such a staggered orbital current. We discuss experimental constraints on the DDW states in light of our theoretical predictions.