Can Orbital-Selective Néel Transitions Survive Strong Nonlocal Electronic Correlations?

Spin- or orbital-selective behaviors in correlated electron materials offer rich promise for spintronics or orbitronics phenomena and applications deriving from them. Strong local electronic Coulomb correlations might lead to an orbital-selective Mott state, characterized by the coexistence of localized electrons in some orbitals with itinerant electrons in others. Nonlocal electronic fluctuations are much more entangled in orbital space than the local ones. For this reason, finding orbital-selective phenomena related to nonlocal correlations, such as orbital-selective magnetic transitions, is a challenge. In this Letter, we investigate possibilities to realize an orbital-selective Néel transition (OSNT). We illustrate that stabilizing this state requires a decoupling of magnetic fluctuations in different orbitals, which can only be realized in the absence of Hund's exchange coupling. On the basis of two-orbital calculations for a Hubbard model with different bandwidths we show that the proposed OSNT can be found all the way from the weak to the strong coupling regime. In the weak coupling regime the transition is governed by a Slater mechanism and thus occurs first for the narrow orbital. At strong coupling a Heisenberg mechanism of the OSNT sets in, and the transition occurs first for the wide orbital. Remarkably, at intermediate values of the interaction we find a nontrivial regime of the OSNT, where the Slater mechanism leads to a Néel transition occurring first for the wide orbital. Our work suggests strategies for searching for orbital-selective Néel ordering in real materials in view of possible spin-orbitronics applications.